Anemones are notorious for migrating about the tank. It's possible that the anemone crawled up the heater and was burned when it kicked during the night. I understand that you're new to the hobby, but anemones are an odd bunch and really require a hefty amount of research before purchasing one...
In a functioning clownfish pair, the male is always the smaller of the two. This being said, the clownfish toward the rear of the tank is actually female. The female usually protects the eggs while the male tends to them by aerating them and cleaning them.