I would highly suggest not to put the code in origin to check in case it is not registered with origin. Cuz once you put the code in it will register if it is not. If its been registered there will be a small statement saying the code has already been registered. A way you can check is if you have a origin account, log in and it will shoe you the gamez you have registered.
I won a sims game with a used origin code, called and told them where I got it, and they activated it for me. I may have gotten someone who wasn't familiar with protocol or just in a good mood, but you might try it sometime.