I haven't tried this or heard of it being tried with RFAs, but pointing too much flow at mushrooms can cause them to let go and move away, and you might be able to encourage RFAs to move with that.
Dangling the rock over a bucket with the anemone hanging down towards some water can work- people tend to try that one pretty often. Also, if you keep an eye on the nem, you might see it start to move. They inflate their foot to move around, which makes them easier to pry up.
Prying an anemone has to be done very gently. Any amount of damage to the foot can be serious, and bad damage can kill them. However, if you can get something wiggled under one edge and ease the edge up, the rest of it generally follows pretty easily.
