At least that's what it seems is going on here. There's a brightly (like fresh shell) colored claw hidden aaaaaaalll the way back in his shell, so I'm hoping he's just hiding from all our shouting.
Some things online say certain ones even eat the old exoskeleton for nutrients. So we placed him back in his tank with it nearby in case he does need to do that and I'll guess we'll see if he's okay.
Yeah, when they molt they tend to hide a bit because they're more vulnerable. I once had several hermit crabs, and one of them ended up attacking and killing a couple of the others, by waiting till they molted