yeah, if there is one thing I've learned in the aquarium hobby, be it FW or SW or Reef, if a fish really wants to hide, it WILL find a way to hide.
That said, I don't think its a good idea to just let it disappear, hassle or not, you should make a concerted effort to try and find the fish, because if its dead, it WILL mess up your tank, even more so if he is hidden in the rock work.