I had the assumption that all crabs left their shell when they molt. Just outside of their shell that is.
My Percy (an E) had dug down - but with part of his shell showing. Two days later, the shell was moved and I checked it - only to find EE in it. I did a quick careful dig to see if I could find him. I was sad to find him legless and sad to say smelly. I found his legs - or most of them - not far from his body. It was a sad day.