First, does the cover say that it came with the map pack? I think that was a limited time that it came with the maps. Second, are you sure they didn't include the maps with the game itself? I know that they were having issues with the way they were giving out the code. There was a code (I don't know what it looked like) and you would have to go to an IW website to enter the code. This website would give you another code for the PSN Store.
If you feel that you should have gotten the map pack with the game, contact IW's or Activision's customer support team.
