Sad to say, that's what usually happens when they're about to die. I've seen them blow their crown and grow another. But when they come out of the tube, something is wrong. They can crawl out and relocate to build another tube if they don't like their location, but when you see them out in the tank on the sand bed, it hardly ever ends up good.
How old is the tank and what are the water readings? Was he in a high flow area?
"Life may not be the party we hoped for but while we are here we might as well dance!"