When they are on the sand and get frightened, they will retract and get sand all over themselves, if that is what you are talking about. It is not unusual for it to wander around. It may even move later if it doesn't like where it has been living. They also like a hole to settle in if they can find one. I drilled a hole in a soft rock and mine lives there. I can move it around the tank to where I want it. Here is one of mine trying to eat itself tonight. Crazy.