If you've redeemed your product code, then you've either been e-mailed the product code from origin, or you've gotten your physical copy of the game, opened it, and entered the code inside. (or some variation of either/both)
If you're referring to your pre-order code having already been redeemed, that's a separate code not to be mistaken with the code that proves you've purchased, not pre-ordered, the game.