Re: code already redeemed
Once the code is redeemed it is forever tied to an account on Origin, except in rare instances of errors and such. Most likely if you don't see the game in your Origin games, then you have a different account with Origin, IE different email, and the game is unlocked on that account. If you don't remember what the account is, then you can go over to official website help page, EAhelp and chat with an customer service rep and they can maybe track down the account and help you merge it if that is your wish.
If you don't have another account, then you still need to go over to EAHelp and discuss it with a CSrep as they are the only ones to able to deal with account issues.
Oh, and you can get help with EA over on Twitter, but I don't use it so have no clue exactly how to do it, but I assume you visit their twitter page and tweet at them.....