Can a Wraith have no shimmer?

Just played a match in swamp against a wraith who hooked me, cloaked, stood by the hook and then his shimmer disappeared. I knew he was there so I wiggled but some idiot still came to unhook and the wraith of course uncloaked and downed me. In post game I checked and he had no add ons and no Insidious. What was the deal? Was he cheating somehow?