I concure, I aggrivated one of my pistols trying to reach a coral frag behind my LR. I could jut bearly touch it with my fingers so it took ma a while to get a hold. The whole time I had a pistol shrimp popping away like a fiend, every bit as fast as a mantis. If the little bastard had left me alone I wouldn't have taken nearly as long, but with him right next to my hand I couldn't help but twitch for each pop. It was like the doctor was playing drums on my knee, but it was my fingers.
Its highly unlikely that your hichhiker is large enough to do any real damage, that would be one nice sized stomadopod. more likely that if its a mantis you wouldn't get popped by it moving your rock around. IF you did get struck I would imagine it would be something requiring no more than a band-aid, if it even broke the skin. Unfortunately though if by rubber gloves you mean kitchen like gloves, you aren't going to get much protection.