there was an issue to the east somewhere (might have been Ohio) where money was found in a house. It too was ruled it belonged to the prior owners of the house as it was not abandoned property but simply misplaced property. Basically there was no intent to convey title of the money so it remained the property of the person that put it there.
There have been several cases sprinkled throughout the country that center on lost, abandoned or misplaced property.
The case I was thinking of (and it could have been Ohio although my feeling is it was farther west) involved items hidden behind the walls of a house by the original owner of the house. The items were discovered when the new owners of the house renovated the home. The original owner had died and the heirs were the ones who sold the house but then the heirs claimed ownership of the found items.
I can't remember all of the details (obviously

), but I think there was a thread on this forum that dealt with this. Maybe in the Real Estate section of the forum?
Anyway, it is always important to know all facts. I even hesitate to absolutely say that the artist retains the copyrights, without knowing all that is involved.
If HuskerT is looking for a clearer answer, he should probably sit down with an attorney in his area to review all of the known facts.
(as a note: for me, Ohio is to the south

)