Well can they escape of coarse they can, now will they? prob not. think about what it would take for them to move the tub out, they would have to either anchor themselves to the rack on top or the tub on the bottom and push while maintaining grip on the tub and top at the same time and move it the correct way, also while not getting their own body in the way. also they would have to have the strength to do so also, a hatchling isn't moving a 6qt tub no matter what.

Their not intelligent animals, I've never herd of someones snake figuring out how to do that. don't worry about it. escape stories always start with "someone left the tub open a little and.....".