Eloboosters/Buying accounts

So I just played with a Riven who fed the CRAP out of top lane yet never built a single defensive item. Pretty common right? Well thing is this Riven is a Diamond 5 playing with low/mid golds and still gets manhandled. Ok maybe he had a bad game, so I look at his LoLKing and his elo has only been higher than 0 LP once in the past month. Was like "ok maybe he doesn't play much anymore". Checked his match history and he plays several games a day and has only won 1 of his last 10 games, the others in which he fed grotesquely. I am 99% sure this guy either bought his account or got boosted by someone because there is no way he is Diamond or even Platinum material. I really hope he gets banned because the people in my game all reported him for boosting.