Lol, I know it's not a 'hamster/gerbil' but I once had a little puppy that always ended up 'disappearing'
My dog had like, 9 puppies, and we had them in the kitchen (One of them died because it didn't have an a**s. WTF). So, anyways, we had those 'baby-gates' in the doors so they couldn't get out.
However, one puppy (Which I named 'Houdini'... of course), always managed to somehow
Climb over the gate... We saw her do this like, twice.
P.S. If you don't know what I mean by a baby-gate, here's a picture