they will totally eat their tails and it is just so...weird! i haven't had one eat its own tail (that i know of) but i had one that ate its cagemate's tail and one that dropped and i never found the tail so i assume it was eaten. the cagemate that ate the dropped tail saw it wiggling on the ground and pounced on it like it had found the tastiest prize piece of meat it had ever seen--by the time i had the cage open it had already halfway consumed it so i just let him have it rather than attempt to pull it out of his mouth/throat.

anyhow, it's no big deal really. cresteds drop their tails all the time, sometimes for no apparent reason. i know it is upsetting the first time you experience it, but for the gecko it isn't really a huge deal at all.

just make sure that the enclosure is kept nice and clean while the tail nub heals up. it should start to close up quickly and shouldn't be raw anymore after the first 48 hours or so. your gecko will be off balance for the first few days while he adjusts to not having the weight of his tail and not having the tail pad back there to catch himself with. i'd advise not handling him for the next few days in order to reduce stress and let him adjust and heal up.