No offense but, the only way you could have "not" seen him for weeks is if you only have about 4 lbs of LR.
So I bought 40 lbs of LR from a guy on craigs list. Over the following weeks this is what I found: about 30-50 tiny starfish that took weeks to identify the different colors, a nassarius snail, sea squirts, feather dusters, what looks at this time like a mini maxi carpet nem(Joker colors: dark purple and toxic green) which I now have 3 of, some kind of encrusting sponge, brittle stars, 2 types of mushrooms, some bland zoas, so many pods I had to get a dragonet (it would've been a crime not to), and about a month ago I spotted a lonely stomatella. I have had the LR for about 3 months now.
See, if it is a new tank, the stomatella would have stayed on the rocks because there was no food for him elsewhere in the tank. If it is a seasoned tank, then you probably have other stuff that you know is in there. Therefore, you are looking for the other stuff and not the stomatella and could have been overlooking him the whole time. Look at how small he is, then ask how big he probably was when he was a juvenile. Could you have missed a juvenile?