No Cerberus Netwrok code in sealed copy

I bought the game a while ago as part of the Mass Effect Trilogy box set and when I opened the second game the little bit of paper which is supposed to have the code on it was nowhere to be found. Is there anything I can do that doesn't have me buy the promo pack (as it was meant to be included)? I contacted the seller and told him about it, but they are not responding and I am afraid I have waited too long. As the game was sealed I did not expect there to be a problem... Hope someone can help!