If you wanted to keep your license, why did you return it? If you could buy the game and return it within 10 days and keep playing for a month, there wouldn't be much reason not to return it. Most games get boring after about a month, and it would sure be better than downloading and deleting a demo.
They aren't getting a 5 week loan, the bandwidth they are saving from not having you play while you wait for your cheque in the mail is worth beans. You got to play the game enough to know you didnt want it, and they are gaining nothing from this, and in fact losing money on the whole thing. Cry more.