He's just popped out and shed its shell!!!!
You can go weeks and sometimes months without seeing nocturnal shrimp. I have 5 peppermints in my tank that I haven't seen for probably 2 months, and a pistol shrimp that I haven't seen in 6 months, but I know he's there because he moves a lot of sand around.
Other than a CUC there really are no benefits. I got the pistol to keep the sand bed stirred up and partner up with my gobie (which has since died), and the peppermint shrimp were added to rid my tank of aptaisa which they did.