Your wish came true althea. The name of the last person to attack the boss is listed on the page where you choose whether to train strength or defense - check right hand side.
Antilles, don't sound so guilty for making a valuable point of strategy. There ARE some people who purposely play this thieving way to the point of not having a life.
The quickest, most efficient way to know who is in your boss level range is to click "Player Attack," remember the names (or jot them down) and when you see who's online you won't need to waste all that time.
Finally, the game developer has indeed provided a way later on to gain extra energy. Of course if you're not premium and the drops are less frequent you may have to kill that particular boss more times. But I'm sure you'll all find it worth the effort.