You need to consider the lighting you are using for that particular species of anemone. All anemones are different and need different amounts of light. You could be using a light that is too strong for that species of anemone, that could be why this anemone is hiding under the rock. I suggest in future you do research before you buy so you can set up the tank to suit the species your going to add. I would suggest changing your lighting to a less powerful light source, this might help your problem.
And by the way, is by trash him you mean leave it to die or kill it i suggest you dont bother to keep any further marine species as you clearly dont understand how to care for them.