Haha, corns are master escape artists, aren't they? I learned the hard way not to keep them in tanks with anything less than a sliding, locking lid (ie. Zilla brand cages from PetSmart). I tried the tops with the little clamps and stuff. Poof! Gone! Our rack that our corns are in have very tight fitting tubs. They are a pain to pull out, but I have yet to have one escape from them.

Don't give up hope, though. I had a yearling corn that disappeared for about 4 months. Never saw the slightest trace of her. People who live in the upstairs half of the duplex found her in their bathroom.

One trick you might try is lining the floor against the walls with double sided tape. Works sometimes.