People abusing the system to get the GP skin.

I was just in a game where the guy selected GP then afked for the entire game didnt even buy items. Things like this are happening because riot said "if you own Gangplank and play a matchmade game with him during the event you get the captain skin for free". Now something needs to be done to deter people from afking and ruining the experience for the players who are trying to have a good time and win. I suggest that when there is a GP in the game and he shows as left the game that he doesnt get credit for the game. As for the people who would then just move periodically so they dont leave the game Im not sure since im not sure if Riot can track things like that :/ maybe something like if the person gets the afk notification more than 2 times that game gets disqualified as a game towards the gp skin.