That’s a very fair point - and while with exception of lithographs, photography, etc. most art really is unique, but there are loads of artists whose art, while

That’s a very fair point - and while with exception of lithographs, photography, etc. most art really is unique, but there are loads of artists whose art, while unique, would be hard to identify as a stolen to us layman - for example Monet painted ~250 paintings of water lilies alone, many of which trade hands in private sales, if for some reason I were to be at a Nigerian central banker’s home and he and a Monet water lilies was on the wall, I would have no idea if that was one of the stolen ones (or a fake for that matter)