Sorry to bump an old thread but i found this in my e-mail when I bought my second copy for my wife after I had been playing for a year or two.
http://i.imgur.com/wD6v7An.png
Proof that when ordered, you received the activation key and the bonus key. I remember this clearly because you had the option to pay an extra $5? I think it was only $5 for the digital download service if you didn't want to wait for the physical copy to comes in the mail.
Sorry bud but it's not SE's fault. The person you bought the game from used the digital code that was sent to them. They owe you, not SE.