And depending on the location, you may not know it when it does. At least for a while. Mine was really big and sticking way out for a couple of weeks, then it retracted a bit. After a few days of this I got a little worried. I looked in the cave where the foot was attached and I could see some tentacles hanging down behind that looked different, like they weren't part of the same critter... they weren't.
After about a week or so of this they suddenly both started to wander around the tank. Neither half ever came back to the original spot, though it hadn't moved since the day I introduced it.