I had one attached to a live rock I got, that was transported, and left in a rubbermaid container with 75lbs of other rocks in tank water with no heater for about 24 hours..... it was smashed under various rocks, and then left in the container with no light or water for 2 more days after many of the rocks had already been added to a tank. I decided to go ahead and use all the rock, so I fished it out (still not knowing the anemone was on the rock) and threw it in the tank one day, and within a few days I noticed it on there...... looked like an old bandaid barely clinging onto the side of the rock..... and I wasn't even sure what it was, but thought about removing it and never did, instead opting to allow the clean-up crew a chance to take care of it.
Long story even longer..... it is now a very nice Rock-Flower Anemone that is about 4x the size it was in it's shriveled up state on the cold/dry rock. These things are pretty hardy......