Unranked player in G1-P4 ranked game?

I am curious to how Riot balances MMR. I was just matched with a player who has never played a ranked game before. He proceeds to play Garen top with ignite and rushes a Warmog's. Then proceeds to massively feed a Fiora. I understand that in order to be placed you get matched with various ranks, but why would it start with high gold/low plat MMR? Everyone else in the game was high gold/low plat.