Xenia goes through cycles in the wild, and in tanks. It will die, so you think, and leave a gooey slim where it was. However, after some time, it will regrow from the foot that was left. There's actually some articles about this where it happens in the wild. Scientists still don't know what/why it does it. So, if any is left where it was on the rock, give it a couple weeks, it could grow back if it wasn't stung or if nothing cleans it up for you. When I moved I peeled it off the glass where it was growing, but didn't get it all. After about a month it shot sprouts and I have it again. Good luck!