I have used the bristle worm traps as well, it didn't work for me either. Arrow crabs work too, but I have heard they will eat small fish and shrimp if they can catch them. If you have not already caught it try taking the rock out of water. The worm will come out looking for water. Make sure though you don't have any corals or anything on the rock. Or try a freshwater dip. Put the rock in freshwater for a while. The worm will come out because of the water conditions. Note: This will kill anything on the LR, so if you have anything important on the rock do not do it. Hope you catch the worm.