I have two bone - headed mistakes that come to mind. On my old aio tank i was tinkering with equipment, and accidently submerged my ato line. About an hour later i noticed ato kicking on about every 5 minutes. It was siphoning tank water back to my freshly filled top off container. Luckily i didnt flood the house, but salinity dropped alot, and the whole tank was mad!
Second time was in my 75. I was trying to rescape/move a lg anemone that was taking up too much of the prime real estate...i had a rock slide and smashed the disc part of the nem between two rocks. He was definitely injured, and quite angry for about 2 weeks, but made a full recovery.
As delicate as these creatures are, they're also surprisingly tough. Hopefully yours will recover!