I'm not sure if you've had a conversation with the scammer in question, but he posted something on EPVP where he requested I send him a trade offer for the boost. Seeing that, I decided to provide additional info.
For reference, he posted a picture of my match history (Imgur: The most awesome images on the Internet) and said he's the one playing the games. Look at the dates of the matches, and look at the day the trade was made. Notice how it's way after?
Now please pay close attention to the champions being played. Here is a screenshot for reference.
This is where it gets interesting. This is my account's most played champions, the ones I main, you can see the order from most played to least played.
Notice something? Exact same champions. That's because I'VE BEEN PLAYING ON THE ACCOUNT. The guy played the first day, didn't play for 4 days, so I took control of the account and started playing myself. Please ban this fraud.
Notice the summoner placement. Notice my penchant for challenging smite on anything. If needed, I can show match histories from further back from when I was climbing to show these things match.