Hermits day out?

[Rogue951]

I have a couple large red hermits for sump cleanup. Today I came home to one completely put of it's shell, climbing around the return pump. Anyone else have this happen?
Looked funny naked. Very much alive although his tail end is shrunken so I think I'll have to start throwing some food his way.
Good sign though, I don't have a lot of waste getting to the sump....
Anyway I put his shell next to him and he went right back in.
Shell isn't too small, he can completely recede into it. And the hermits are in individual compartments so he got no one to fight with.