How do I report someone if I find out they were boosting after the game?
I get destroyed in lane by a random riven. I op.gg her afterwards and figure out the account has a 100% winrate on a select few champions and only has 9 matches on it history. I go to the profile on the league client and it hasn't been active since june 2016 when it was a support/adc main in Bronze with around a 50% winrate. Fast forward 6-7 months and it's going perfect in ranked with scores reaching as high as 30/4 on riven. Keep in mind that it goes straight from support/adc to playing top in ranked. There isn't a single riven game where it's a normal since the account became active again.
Wasn't active for 6 months. Immediately starts up again. Completely different role and champion pool. Has minimum of 50% kill participation in all games. Hard carries 9 games in a row.
So how do I report for this after I've already closed the post game lobby?