As per usual with these posts, innocence is unlikely, but I'll upvote to hopefully get a Rioter response.
If there's no game associated with the ban then Riot did not ban you for typing in that game.
Maybe you scripted, or maybe a credit card used on the account was called in to Riot saying an unauthorized purchase was made (in this case you can likely get a manual review), or maybe you did get a reform card and are simply pretending there is none so nobody will pressure you to reveal what you said in game.
There's too many unknown factors for us players on the boards. Your best bet is to submit a support ticket and see what Riot says.
http://support.riotgames.com/