Yeah, from what I've read it's pretty much impossible to completely remove the copper from the rock. I posted a bunch of threads here and on RC about copper removal for the tank itself, and the responses I've received, you can save the tank by draining it and giving it a good rub-down/scrub with vinegar to release the 'sticky' copper med (this apparently goes for glass and acrylic tanks). Mr. X on this site stated that he had treated a tank with copper and was still able to keep inverts eventually.
You can buy filter pads that will remove the trace copper, but they're a little expensive. Also if you're using API test kit, that test for one kind of copper, Salifert or others will test for the other kind (chelated and non-chelated). I tested one tank and API said zero, Salifert said 0.5 ppm