Silver in Plat?

Recently I was playing a ranked game and someone said that one of his teamates was Silver 1. Curious me looked one lolnexus and lolking etc. and he was. I was just wondering the reason why he was in our game and if it was a bug or something. I looked at his recent games and it said that he played enough where it wouldn't decay him so I was just wondering if something was up. I don't know if this was the right place to report it, but I guess if it was something I better just go forth.