Nuclear Bombs - What was still around..

[Olefin]

Would come down to how the B-52 came down. If you come down nose first like Flight 93 did then there wont be anything bigger than small bits. If you come down out of fuel in a belly landing attempt and screw it up (think hit a building and tear off a wing or the side of a hill or the plane tumbles) then you would have large pieces of very identifiable wreckage

or for that matter go down where the plane partially ends up in lake or river and all that is sticking out is the tail