Not sure how long harlequins take, but, I know time varies. My cleaners take one day. My mantis takes weeks. Remember that some shrimp go into hiding after a molt while the new exoskeleton matures...
How big is the tank? Keep your eyes open. Hopefully it'll pop up...
150gal. It's kind of like trying to find a needle in a haystack, lol. Hopefully he will pop back up I still have plenty of starfish that he needs to eat.