You can't get them back. That is why you have to be absolutely positive when you want to train another role or SA for a player, otherwise you are just throwing skill points down the drain
I know I can't get them back. That's why I'm making a suggestion. In real life you can change your mind you know. "Hey Mike I want you to work hard on free kicks" (1 month later) hey mike, scratch that work on penalty kicks instead. Seem pretty simple to me.