To be fair to whoever wrote the textbook, it is plausible that high officials and courtiers in the Qing empire were not particularly cognisant of where exactly the silver being spent on opium was going, or what was being done with it, and the quote doesn't suggest that they didn't know how widespread opium consumption was in the empire.

Let's start with that last part. Frankly, it would be impossible for them not to have noticed by 1839, as one of the key events motivating the Daoguang Emperor's anti-opium crackdown in 1838, in the wake of a failed attempt by a group officials to get opium legalised in 1836, was the discovery of a stash of opium in the Forbidden City itself. That Cantonese opium pedlars operated across the country was quite well-known (since the only port of entry for the drug, at least from maritime sources, was Canton, yet opium was being smoked far inland), and it's even been suggested that the Daoguang Emperor may have smoked it in his youth – though this is thanks to the ambiguity as to the term 煙 yan, which is simply 'smoke' and can refer to tobacco or opium. Still, there is something tantalising about the idea that the Daoguang Emperor was not inexperienced with the effects of opium when he became a prohibitionist. Who knows? Maybe that stash found in 1838 was a leftover from his wilder teenage years...

The Qing were also evidently quite aware that silver was leaving the country thanks to opium, or at least believed so. Both Man-Houng Lin and Richard von Glahn have disputed this, Lin arguing that the silver drain was the result of global market trends, von Glahn on the basis that there was no silver drain and that the perceived drain in silver was the result of an incorrect inference from a downturn in the relative value of copper coinage. Whatever the case may be in terms of the actual economic issues, from a contemporary perceptions point of view, that opium was being blamed for a drain on China's precious metal reserves was clear, and both the legalisation and prohibition camps both argued their cases on the basis that they were offering a solution to that problem: the prohibitionists by cutting opium imports outright, the legalisationists by regulating and taxing it.

And it was pretty clear who was getting the silver: British (and American) merchants selling opium through their intermediaries. While Lin Zexu's attacks on the Western merchants in Canton in 1839 were unprecedented, their targeting was by no means arbitrary, as there were plenty in the Qing court who recognised who it was that were the origin of the stream of opium making its way into the country.

But, as noted, it's not wholly certain that the Qing court knew how that silver was being used. /u/pangerandipanagara wrote a great post on the Qing court's knowledge of Britain a couple of years ago that illustrates how in the run-up to the Opium War, the Qing really didn't know that much about Britain at all. In 1842, three years into the Opium War, the Daoguang Emperor still had no idea where it was! But I suppose we need to distinguish 'the Qing' from 'the Chinese' here – as the latter part of this earlier post of mine details, several Chinese travellers went to Britain and left accounts, and plenty more whose accounts do not survive nevertheless had their findings compiled by Cantonese scholars. Some such accounts do in fact describe facets of the industrial revolution, so clearly by the 1830s there were those in China who did know about Britain's economic boom. However, I've found little to suggest that they connected it to the opium trade. More importantly, it does not appear that southern scholarship on the Westerners found much of an audience at the capital in Beijing, given the general lack of awareness of British military capabilities held by virtually all the Qing commanders in the Opium War, whose experience was mostly earned in Central Asia.

And so for that reason, I do have to stamp a seal of 'technically correct' on at least the second half of that quote from the textbook, because although the Qing did see that a huge amount of silver was leaving the country and entering foreign hands, that step of linking the perceived silver drain from China to the apparent economic success of Britain and America does not seem to have been made, at least to my knowledge. Moreover, even if it was, it would have been a link made by southern scholars with little reputation at the imperial court.

Sources, Notes and References

1. Zheng Yangwen, The Social Life of Opium in China (2005)
2. Stephen R. Platt, Imperial Twilight: The Opium War and the End of China’s Last Golden Age (2018)
3. James Polachek, The Inner Opium War (1992)
4. Man-Houng Lin, China Upside Down: Currency, Society and Ideologies, 1808-1856 (2006)
5. Richard von Glahn, 'Economic Depression and the Silver Question in Nineteenth-Century China' (2017)
6. Mao Haijian, The Qing Empire and the Opium War: The Collapse of the Heavenly Dynasty (1995)