I don't want your mantis, but here's a good trick. Take a 20oz. plastic soda bottle. Thoroughly wash and rinse it. Cut the top off, about 2.5", invert it back into the bottle and silicon it together. The next day after it has cured drop in a piece of raw shrimp and sink it. Within a couple of days you should have your mantis. Sometimes it takes a few different baits to get them.
There is always the , remove the rock it is in method. This works if it is a rock you can get to. Simply take the rock he is in and dunk it into a bucket of freshwater. In about 30 seconds they come running out. One way to spot where they are living is to feed the tank with live brine shrimp. Sit back and just wait for them to come out to feed. That's how I spotted my first mantis. Hope that helps!