He was about twice as big as when I got him so I didn't worry too much. He disappeared back into the sand bed.
Tonite, I saw him up on the glass and he literally let go, like those small brittles do, to float to a new area, then disappeared. I think he will be fine.
FWIW, I have egg crate under the shallow sandbed. It would appear that the life forms seem to have some protection. I'm not after a nitrate reducing sandbed as I have ample rock to do that.