Crayfish and the like are "Houdini's" when it comes to escaping. a while back I had a crayfish that had virtually disappeared from my tank, a long time had passed ,then I seen his shell behind the tank (55 gallon) and then the next crayfish I purchased i made sure to seal my tank. I've had betas jump out and not quite dry up and threw them back in the tank and it made a come back.