How come artworks are always being discovered in collections?

>>2398424
Museums binge buy shit from collectors and resellers when they get some budget allocation or donations.
They also get a lot of shit donated in. They're usually understaffed, bureaucratic or just outright money laundering, so finding out what they have and if it's legit does take some time.

A lot of items come to them without much information, and the provenance of a lot of artworks that are attested in writing often aren't kept track of and they don't know how it got to certain collectors. Sometimes drawings by artists have sources or purpose that are unknown and needs a lot of investigating and luck. As for documents, it requires a lot of research and even if they might have read something important before they might not have had other necessary information to make much use of it. The the detective-like field of attribution using wide research has only been recently developed.

>>2398424
This isn't every time BUT a lot of times they find a shit ton of pieces of many scrolls that are in no particular order. It can take hundreds of years to piece these fragments by hand. A lot of them still incomplete but can be cross referenced with another, separate incomplete scroll which is obscure and only known by a handful of people.

People are only now starting to scan these tiny fragments and having a computer piece them together which will be much faster but I don't know how wide spread its use is.