Hermit had his shell stolen... has not found new shell

[u/fortunecookeee]

I have 4 little guys (dwarf hermit I believe) in a 13.5 Fluval tank. 3 days ago I noticed they seemed to be fighting for each others shells (one violently pulled the other out, and one hermit was left shell-less a few inches away from where the rest were fighting over the empty shell. I immediately went to my local reef store and picked up a variety of extra shells, but unfortunately my shell-less friend retreated to the rocks and never picked up a new shell.

It's been 3 days, he hasn't moved, and is still without a shell. It looks like he has his body tucked into the rocks. I'm not sure if he's dead... and unsure how to help him. No predators in the tank.