I'm quite sure that many collectors would buy it on the black market.
honestly there aren't many collectors who would buy it for a very high sum and then keep it in a dark cellar all for themseves. for most people that buy a real munch/rembrant whatever is one of the best aspects of it to be boost. believ me this are facts. my aunt is specialized on stolen art, it's her job, so that's were I get my info. besides I myself work part-time for a museum.
so either the pictures will appear in a few years when the thieves realize it's impossible to sell them or artnapping - but this would no museum admit officialy