Ok, the original question was modified to get you guys warmed up, so now your brain has warmed up, no excuses that I did not give you enough time to think, so I will now revert the question to its original format,
in that room there are just those two guys, no mice dropping sand no mice either, just 2 blokes, A & B, both know there is a fiver, and it doesn't belong to either of them, and each hopes the other hasn't seen it so that who ever gets the first chance snaps it.
So now if B excuses himself and has to go to the loo, and when he returns, the fiver is missing!
So now who took that Fiver, assuming there were no other people who came into the room during all that time and it was just the two of them, no mice no book worms, just them two and lots of clutter!
so who took the fiver A or B?
Typical religious fanatic, change the story half way through when he realizes the majority have seen through his concocted little story.