Donna, in the forgery trade the provenance (stickers, notes, letters, photos, documents, inscriptions, vague catalogs) are all as important as the artwork itself. There is always the phony story of the gift or purchase or trade into a family that either kept the art quiet and private or simply had no idea what it was worth. The servant who was gifted or paid in art. The mistress who swiped it in anger. And the other common one is that it was "found" at a flea market, garbage dump, garage sale, ruined building, etc.
The willingness to believe that you can get something for nothing, found treasure, etc. is at the heart of the confidence game, and it works all too well in every con game. There is a marvelous series available largely on YouTube called "Fake or Fortune" a British production that goes through this from both angles, authenticating the real and debunking the fake. In fact, the more you learn about the forgery trade, the less remarkable it is that bona fide museums and traders have become seriously skittish. In fact, they've been fooled so often and so spectacularly that you wonder what is actually authentic!
How about if I sell you a forged Bart painting? Can we make a deal? I found it in my garage....