I’m not sure. Maybe you could use your thumbnail and slowly edge it off?
I wish I had the trick to get them to attach to rocks!! I’ve had a beautiful pink ricordia in a container with rubble for two months. It refuses to attach. I thought I had it after three weeks. I removed the rubble it attached to and three days later it was gone. It blew around for while then I didn’t see it. Two weeks later it went floating by, a quarter of the size it was when I bought it. I scoooed it up and it has been in the rubble container for awhile now. Still not attached