My hamster once escaped by chewing through a junction in one of those silly plastic hamster cages (which you should never, ever use). On her way out, she got a small cut in her foot on one of the sharp plastic shards where she broke through. I was able to follow the tiny trail of blood to underneath the bureau that she normally lived on top of. Once I knew where she was, she was easy to lure out with the promise of food and love.