Sorry, I must have missed that post. When I'm on my phone, I miss a lot of posts because it scrolls through quickly.
Black tipped claws are no good. 90% of the time, the hitchhiker crab is a Gorilla Crab or a Xanthid, google those two and see if that's what you've got. Xanthid's come in a wide variety of colors, but their shape when they are scared is very identifiable with the species. When scared, they retract into what looks like a tiny, smooth rectangular stone.