Mantis can and do make clicking noises. The species most often found in TBS rock, N. wennerae, is diurnal so try looking for it when your lights are on. If you do have a mantis eventually it'll poke its head out where you can see it.
My experience with the Gulf pistol shrimp is that they click and pop day and night. They also don't seem to bother anything, at least not that I've noticed.