When my tiger pistol molted he losf his claw and regrew it. I hope this is going on with your postol shrimp, they can also lose their claw by fighting. It had me worried the first time I saw the molted claw and my postal stayed hidden for a while.
It's amazing how seawater creatures can regrow missing parts of his body, it always amazes me, it's surprising. That's one of the reasons I like this hobby, it's always discovering something.