Gorgeous mantis, what a pretty colour! If you can narrow down the rock s/he's living in, I've had success using hypersalinity dips/pours. I saw a mantis on one of my largest pieces of LR and all it took to get the beastie out was pouring high-salinity water (SG ~1.035) over the rock. It took about 60 seconds in all, including removing and replacing the rock. I poured water into the holes, and the mantis dropped right out and into a bucket below. S/he was ID'd as a small species that shouldn't cause trouble, and now lives in my 30g tank along with a pair of maroon clowns. I hear occasional soft clicks, so I imagine s/he's hunting pods, but never see him/her come out.
If you decide not to keep it, see if someone in the mantis forum wants to adopt it - there are always folks looking for a mantis; in a little tank of their own, they can make really neat pets.
