Itsie changed shells yesterday and it was entertaining. After she decided on the new shell (moved in, moved back to her old, checked out other shells, moved into the first one) she kept a leg on the old shell. Then she moved the old shell to a hidey and guarded it.
After a while, I took the old shell, rinsed it in salt water, and put it in the pile. Wouldn't you know after a while that old shell was back in the hidey next to her while she is in the new shell.