information loss

I'm afraid that your question is founded on a false premise. Single, catastrophic events may be dramatic to read about after the fact, but they are not the cause of losing texts. I commend to your attention u/XenophonTheAthenian's post on that museum on the Nile Delta, which deals not merely with that but also how we do lose texts, as well as u/rakony on the House of Wisdom.

Not a case of deliberate damage, but an unfortunate accident - Sir Robert Cotton, an 16th c. English manuscript collector, had his collection donated to the British Museum by his grandson Sir John Cotton at the beginning of the 18th century. The collection had been quite important for having assembled various manuscripts held in the monestaries across England following their dissolution in the middle of the 16th century. Unfortunately, in October 1731, the collection, then residing in Ashburnham House, London, suffered an extensive fire which destroyed a significant portion of the collection. Tragically, the original building where the collection had been kept had been deemed a fire hazard and as such it had been moved to Ashburnham House.

A significant number of manuscripts - anything from Old English manuscripts to early transmissions of biblical texts - had been damaged a number lost entirely, though trying to figure out the full extent of what was lost, damaged, and later actually recoverable seems to be an ongoing study; Andrew Prescott suggests identifying individual manuscripts that were known to be lost to highlight the damage instead of pondering too much on statistics which are unreliable - perhaps the greatest loss was Robert Cotton's personal favourite - a 5th c. Greek illuminated copy of the the Book of Genesis (1).

Some of the texts that survived the fire are notably the only copies that are known to exist - Beowulf is perhaps the most famous example, and you can still see the charring on the edges of the vellum as it barely survived. It is definitely on a much smaller scale to the example you've given with Alexandria, but considering that relatively little Old English material survives, even the loss of individual texts such as the Battle of Maldon is a major setback.

Some useful British Library blog posts about the collection and the tragic fire:

Fire, Fire! The Tragic Burning of the Cotton Library - Medieval Manuscripts Blog - The British Library

Crisp as a Poppadom - Medieval Manuscripts Blog - The British Library

NOTES

(1): Prescott, Andrew, 1997. "'Their Present Miserable State of Cremation': the Restoration of the Cotton Library" in Sir Robert Cotton as Collector: Essays on an Early Stuart Courtier and His Legacy, edited by C.J. Wright. London: British Library Publications, pp. 391-454.

Here are a couple that I'm aware of, as has already been pointed out the destruction of a library does not necessarily mean the loss of the texts it holds, but as humans tend to prefer dramatic events I'll outline two below:

Fatimid libraries:

The Royal libraries of the Fatimids included a reported 1.6 million books at their peak (al-Maqrizi), although this includes duplicate books including 1,200 copies of the History by al-Tabari and 2,400 Qurans. Ibn Abi Tayyi declared the libraries a wonder of the world. It should be noted that these numbers come from Fatimid sources and so may well be exaggerated. What we have a little more information on is the Dar al-'Ilm or House of Knowledge, it had an annual budget of 257 dinar and allowed anyone who wished to read and copy any books present. In 1068 CE rival factions within the Fatimid Caliphate looted the libraries in protest for being unpaid or underpaid following financial difficulty for the Caliphate. Then Caliph al-Mustansir also sold off many of these books to make up the shortfall in revenue. The diminished libraries did survive though. It wasn't until the fall of the Fatimid Caliphate that the libraries were completely destroyed by Saladin in the early 1170s. There is debate on the exact fate of the books under Saladin with reports ranging from every book being sold, to some sold and others gifted to those interested in them, to repurposing the leather and destroying the contents, to a systematic destruction of any books on Ismaili literature and history. (He viewed the Ismailis as heretics although he was far more critical of the Nizari "Assassins" than the Musta'li, deeming them "enemies of Islam" and "heretical and murderous" in a letter to the Abbasid Caliph.)

Nizari libraries:

'Ata-Malik Juwayni wrote in reference to Rukn al-Din Khwarshah the final Nizari Imam to control Alamut* "He and his followers were kicked to a pulp and then put to the sword; and of him and his stock no trace was left." **

This was during the reign of Hulagu Khan in 1256. Rukn al-Din wanted to show submission to the Mongols as he was well aware he stood no chance in a direct war with them. In accordance with Hulagu's command he started to dismantle Alamut, Maymundiz and Lambsars Castle, starting by removing battlements and towers. Hulagu saw this as a delaying tactic and that Rukn al-Din was waiting for winter when he could oppose Hulagu's demands. The Mongols attacked and Rukn al-Din surrendered on the 12th day of a siege on Maymundiz. With the Imam under their control the Mongols got him to command the surrender of several other fortresses including Alamut.

After Alamut's surrender it was ransacked by the Mongols and everything not taken was burnt including much of the contents of it's library.

The exact size of the library at Alamut is unkown beyond it being significant. Perhaps most famously Nasir al-Din al-Tusi was a resident in one of the Nizari fortressess surrendered in what is now Iran, and joined Hulagu's court after Alamut's destruction.

*There is evidence to suggest the Nizaris retook Alamut on at least 5 occasions but never for any great amount of time before being retaken by the Mongols.

** It should also be noted that Juwayni exhibits anti Ismaili and pro Mongol bias with David Ayalon calling his account "nauseating" and "servile" to the Mongols.

Sources:

Halm, Heinz, The Fatimids and their Traditions of Learning (London: I.B. Taurus & Co. Ltd., 1997)

Daftary, Farhad, A Short History of the Isma‘ilis, Edinburgh, 1998

Daftary, Farhad, The Ismailis Their History and Doctrines, Cambridge: Cambridge University Press, 1990

Verde, Tom. Cairo's House of Knowledge, 70, 20-25, Smithsonian libraries, 2019

Lewis, Bernard, "Saladin and the Assassins", Bulletin of the School of Oriental and African Studies, University of London, 15(2), 239-245.

Bora, F (2015) Did Ṣalāḥ al-Dīn Destroy the Fatimids' Books? An Historiographical Enquiry. Journal of the Royal Asiatic Society, 25 (1). pp. 21-39. ISSN 1356-1863

Virani, Shafique N. “The Eagle Returns: Evidence of Continued Ismāʿīlī Activity at Alamūt and in the South Caspian Region following the Mongol Conquests.” In Journal of the American Oriental Society 123, no. 2 (2003): 351-370.

'Ala' al-Din 'Ata-Malik Juwayni, Ta'rikh-i Jahangushay, ed. Mirza Muhammad Qazwini, 3 vols. (Leiden: E. J. Brill, 1912-1937), 3: 275; trans John A. Boyle, The History of the World Conqueror, 2 vols. (Cambridge, Mass.: Harvard University Press, 1958), 2: 723   David Morgan, “Persian Historians and the Mongols,” in Medieval Historical Writing in the Christian and Islamic Worlds, ed. D. Morgan (London: School of Oriental and African Studies, Univ. of London, 1982), 114; David Ayalon, “The Great Yasa of Chingiz Khan: A Re-examination,” Studia Islamica 33 (1971): 133