Nice! from my experience you are the lucky holder of aptasia eating peppermint shrimps! i did have 3 myself and they do wonders! at first they would hide during the day and come out a little at night. they are shy in a new environment and when they molt. you may not see them for days!
after a while i saw them hang around in dark places during the day. they were more visible. and about 1 month later, it would come out to feed when i fed the fish.
if you truly want to see if they are around. wait at night, and use a RED light and look for them. you will probably see them doing their thing (they cannot see red light, like most marine organisms)