Peppermint shrimp

[ickmagnet]

I have an apitasia outbreak in my tank and it will be too hard to inject all of them so i bought 6 peppermint shrimp a few days ago hoping that they would take care of the problem. Since I dropped them in my tank, they have completely vanished. Either they are all dead/eaten or very good at hiding. I've looked all over the tank and can't find them. Is this normal?

here are the suspects:
powder Blue (unlikely)
blue legged crab (too slow)
green wrasse (maybe, but has never touched any other invert)
yellow tang (way too friendly)
purple tang (unlikely)
three clowns (probably not)
couple of damsels (doubt it)
carpet anemone or bubble tip (maybe one but all 6 would not be stupid enough to jump into their mouths)
long spiked sea urchin (possibly but too slow)
Blue regal (again, probably not any of my tangs)

Any ideas?