how can I identify which opponent violated fair play?

they didnt tell you for a reason, i think its about their privacy policy.

The thing is as well it was bullet chess, why would anyone even bother with that mode cheating wise?

I think when a user gets banned for fair play policy, the site returns all the elo to all the players who  lost to the banned user regardless of whatever or however the match was.     

Fair enough. I just wonder if there's a way of finding out who it was.

Go through your archive and look for the red circle with a line through it.

Thank you @martin_stahl that worked. I now know who it was.

I care, hence the thread

is there any way to filter it? that would be a very cool addition, and im curious as ive had quite a few elo returrns

You could filter on losses

Skeeby Dee

ive had quite a few of them you see...