I just also had a emerald crab die or molt????????
Im not sure what
It looked like a whole crab just whiter and it did not seem hollow. But just in case I left him in the tank, to let the clean up crew take care of him if he was dead.
A few days latter I noticed the shell looked cracked and hollow, but im still not sure if it molted or if my clean up crew did a great job of eating him up,
If i were you i would leave it in the tank for a week just incase he molted.