Seeing as account hacks are a very serious issue, I wanted our team to take a hard look at this. Having your account compromised is arguably the worst experience you can have in League of Legends. If Player Support had added insult to injury by banning a player who legitimately had their account ripped from them, I wanted us to publicly apologize for the mistake and get this fixed immediately.
The OP purchased a significant amount of Riot points in November via PayPal. It was actually an amount higher than the $400 claimed (and is currently subject to a chargeback). Approximately four weeks ago, the OP posted details for the sale of his account to several sales websites, including ownedcore.com. (Links withheld as the posts contain personal info). The sales listed the inventory of the account, which we then matched with the OP's account.
We received a ticket at the beginning of January from a player claiming that the OP offered to sell them the account. The buyer agreed, paid, and never received the account from the OP. The buyer included screenshots of the PayPal transaction, as well as their Skype conversation with the OP. Without giving personal details, the Skype name, account e-mail address, e-mail address listed in the selling listings, and the PayPal e-mail address all connect to each other. The IP address on the OP's account has remained constant throughout this entire time period.
I hope that clears this up a bit. However, the real reason for this post is to underscore how important account theft is to us. This is an incredibly awful thing to go through. If you are hacked, contact Player Support immediately, and we'll work with you to get your account back, in the exact same shape it was in before it was stolen. Thanks for putting up with my wall of text.