Welcome to RC!!
I personally do not have a Lobo, but possibly something in your clean up crew munched on it....Really the first thing I thought of was a hermit crab died or was killed, fell on it, and something got on top of it and used your Lobo as a dinner plate. Just thinking aloud.....
The second pic looks like an Aptasia, I cant be certain, the pics a little dark. Google Aptasia or Glass Anenome and look at some pictures, that should help. If it is then yes you want to get rid of them. There are products to use, do not just go in cutting or pulling. They can release spores or something like that through out the tank, then you will have a real problem bc they will be every where. I have used Aptasia X and believe it works pretty good, others chime in please!
One other thought...If that is an Aptasia, is it close to your Lobo?