Aren't these companion certs viewable somewhere on the website? I can't seem to find the one from the SM Platinum card.
As a side note, at some point over the past couple of months, it appears that the free checked bag benefit of my platinum card no longer "stacks" with the free bags associated with medallion status. I used to show 3 bags for free, now just the standard 2. Not that big of a deal to me personally, but it does seem as if AmEx + DL are rolling back benefits of these cards.
I'd be more concerned if I wasn't going to drop this card like a bad habit soon.