Trying to report a player who somehow avoided the system.

So, I know that this player definitely avoided a ban using tactics and one of his allies to constantly stand up for him. This player was a MASTER-LEVEL PLAYER, and they AFK'd after the match was "over" to them, at one point running mid and feeding a kill to the enemy team because they were on such low health. They also AFK'd in the enemy's jungle for well over 10 minutes. I have the game filmed as well, and I'd like to submit it to riot because this kind of behavior out of any player is unacceptable. And for them to have gotten away with it and just blamed their support for everything is absolutely frustrating.