Jhin W exploit

I just finished a game where the Jhin openly admitted to exploiting to win. How is this still possible? I don't want to start a witch-hunt for this one guy, but I just want Riot to know that this is still an issue. I don't know what they can do about it, but it's a problem. I don't know how often this occurs, this is the first time its happened to me.

Below is the clip of the moment we all got hit. You can see that Nami, Twitch, Udyr, and TF all stop (Vlad keeps going for a bit). Again, I don't want a witch-hunt, this is just evidence. If you look at the scoreboard and then the 'objective-tracker 3000' at the bottom you can see that we had been winning up until then. Then we all crash and they take over.

I don't know how to find chat logs, but if someone knows how to access them the Jhin openly claims that he is going to do this at the start of the game, then brags about it after we reconnect.

Thank you for taking the time to read this, and I hope this issue gets addressed, as it really ruined my day.