Lol, it's probably like your video where you 'killed Bajan'. You had a video labeled "I KILLED BAJANCANADIAN" and it was really just a lobby with him in it.
There is no way you possibly could've killed leafy. The best I can imagine is you somehow managed to hit him once and when he got banned you got the points for it.
Also, if you joined the games around the time you joined the forums, you wouldn't have been around when leafy was banned. He was banned june 3rd 2012 (or around then, that was leafy day) and I honestly doubt you were around back then.