Well, you definitely want to get it out, or your stock will start disappearing. They are nasty, but are also very clever, if that trait can be assigned to a shrimp.
Don't try to catch it by hand, because they have a nasty hammer claw that, depending on its size, can break glass, or even the bones in your hand - (that is their reputation) although I haven't heard any actual experiences of that happening to any members here. Of course, it may be hard to grab anyway because of their speed.
Try and trap it. I hear a lot of people try using coke bottles with raw shrimp in it to lure it inside and then grab the bottle. They also sell mantis traps that are a hit or miss. They will catch the first thing that goes in, including hermits.
I have heard methods of injecting carbonated water into their LR hiding places (after the LR is out of the tank of course) to get them out...one even went so far as to drill out the holes in the LR...worked, but a bit extreme.
In any event, best of luck.
