Sounds to me like a piece that was quietly stolen from the museum that it was donated to and that it had a sticker from. (Helps to have the sticker for the authentication that would be required in order for it to fetch much in the market.)
With the ‘finder’ not being publicly identified that makes it a little more likely IMO she could be fencing it for someone.
Tricky, tricky stuff. I didn’t even think about that! It does make sense in a way.. if she is questioned, she can say she purchased it in a mixed bag of stuff. Chances are that sales of this nature don’t keep detailed records of every wooden spoon, book, picture that it sells. You’re a smart cookie, Lurker!