Don't flick him so hard next time you cruel jerk! Jk ;) glad you a. Spotted it and b. Got it out though! Since they can kill lots if things.however im not sure if its a gorilla crab, gorillas have black tips on the end of their pinchers.... from the pic this one appeared not to. But it looked close enough to not risk it.
I don't know what your complete setup entails BUT in the future you could totally throw that guy in a sump or refugium if you wanted to be able to keep it but not have it in your DT