Ranked Matchmaking

Very confused right now. Lost a series game with an unranked player. The match between all 10 players consisted of players from Silver to Plat, majority gold. Needless to say, that individual got pubstomped by the opposing laner/team. Come to think of it, theres been a few other times as well.

Just started playing again a few months before season ended. Was there a change in how provisional games are calculated?

Or is this a case of people purchasing accounts and doing a name change?