Yeah unfortunately taking most of the rock out is usually the only way to catch them and they dont tell you that at the fish store when they are selling them to you. Another one of the reasons damsels are avoided by many.
I know of people who actually bait a tiny hook line and sinker becuase the have trying everything and could not tear down the rocks for various reasons. I do not recommend it obviosly but just goes to show how elusive they can be to catch with a net or trap.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.