I have been really into Ancient civilizations since I was very little but recently I started reading about Rome. I grew interested in the Vestal Virgins and began to read about them. During that, I found an account by a Greek historian (Zosimus) concerning the last vestal virgin, an artifact I had never heard of in an academic source before, and the niece of Theodosius I (named Serena). The legend is recounted here 0490-0510,_Zosimus,_Historia_Nova_(Green_and_Chaplin_AD_1814),_EN.pdf (documentacatholicaomnia.eu) on page 69, 2nd paragraph. Essentially, Serena steals an artifact known as Rhea Silvia’s necklace from a statue inside a temple. I can find no other mention of this artifact (except the claims of this Robin Rivers person who says it can be found in The Sibylline Chronicles but I looked and couldn’t find it), which I find odd as Rhea was the mother of Romulus, the legendary founder.
The questions in bold are the ones I really would like answered if anyone doesn't have the time to do them all. I know these are a lot of questions and I've posted them previously without any answers, but I really am curious. Thank you.
1) Do historians believe the artifact existed based on Zosimus’ account?
Are there other sources on this- either academic or mythological?
Is Zosimus' account considered too biased against Christians to accept it as proof the necklace existed? That after the downfall of Serena and her family, he formed a tale to explain it as the actions of pagan gods on "impious" Christians?
4)If an artifact is lost to time (or hasn't been found), how do historians determine if it likely existed?
And what is the "threshold" historians have when it comes
Well, firstly it should be noted that there is no such thing as an unbiased historian, ancient or modern. All historians serve their own particular desires and agendas. History is a process of mythmaking in its own right, to echo M. David Litwa's How the Gospels Became History (Yale UP, 2018).
Depends on the historian and the artifact in question. In this account though, there are several reasons for considering it ahistorical, not the least of which is the fact that it is all a legendary account of Serena just stealing from a statue of Rhea and then being called out, then being struck with divine punishment for it, in the form of her prophetically seeing her own death in her nightmares (Zosimus, New History 5.38). There is simply no reason, in my opinion, to see it as anything other than polemic. I tend to follow G. E. M. de Ste. Croix and others who have argued that his antichristian agenda led him to entirely invent and fabricate new events or myths about many Christian leaders for his own purposes, something which Christian scribes did in turn as well.
Serena and her family are recorded in other sources, specifically Eunapius, but Zosimus is entirely original on his narrative, outright contradicting Eunapius, and given the polemical nature of his own narrative, we have stronger reason to discount Zosimus.
As for how we determine if some object really existed, we really cannot if there is no good evidence that it existed in the first place. Key examples of such artifacts are those like the Ark of the Covenant, or Mimung, the sword wielded by Dietrich of Bern (Theodoric the Great in legend), Witege, and forged by the legendary smith Wayland. Simply put, legendary artifacts passed down in legend or myth may have existed at some point, and their figures are often historical (Sigurd = Sigebert I; Brynhild = Brunhilda the Visigoth; Gunther = Gundaharius), but the artifacts were either lost or are so waist deep in legend that it no longer even makes sense to talk of them as separate from those legends.
Really, there is no hard metric either. To a large extent it depends on the historian. Some are more generous than others, some are completely skeptical. In some fields, various different methodologies are applied and are in use.
For historical methodology and such, I would suggest the following texts:
Michael J. Salevouris and Conal Furay, The Methods and Skills of History: A Practical Guide (Wiley Blackwell, 2015, fourth ed)
Martha Howell and Walter Prevenier, From Reliable Sources: An Introduction to Historical Methods (Cornell UP, 2001)