Several of mine are doing that on a regular basis, parking during daytime in secure area, moving at the night - there are predators in the tank: puffer and medium-sized hermits. I personally removed the zebra hermit once, when he teared flesh of the turbo - it closed lid not fast enough, and he inserted the big claw as a stopper.
Alive since that.
Moved 2 of these turbos in the safe tank - they are working during day and night - as they want.
Just curious, how cleanup crew is supposed to work, if hermits are attacking snails? What else for a bare bottom tank?
You can easily check, is it alive or not: try to pick it up - if there is resistance - alive, if not - remove, take a look or/and smell, you can't be mistaken.
