This is important to note.
It appears that if you formerly had the Gold Card attached and then upgraded to the iPhone App you still have the Gold Card attached to your account.
DO NOT ever shred your Gold Card, or dispose of it. If you ever have trouble using your saved code or new iPhone Authenticator App, MA will revert you to the Gold Card. I have had a few in-game friends have issues with this over the last year. This is bizarre to me, it seems like upgrading to the new iPhone App should replace the Gold Card completely, But it does not.