OP I just had an issue of sorts recently...while not on my Amex Gold it was on my SPG Luxury. Stayed at a new Marriott hotel...place had only been open for 17 days when I stayed. Nonetheless charged my stay to the SPG Luxury and even Amex's system showed it as Lodging, and even showed my check-in and out date yet the purchase only triggered the 2x bonus instead of the 6x.
Contact Amex and they told me to call back after the statement cuts just to make sure the issue didn't correct itself. It didn't and when they realized it they said that it's probably because the hotel was new and/or the MCC code isn't proper. Nonetheless they requested a copy of the hotel bill which I sent after calling Marriott to obtain. Sent it over to Amex and they corrected the situation by pushing the 4x remaining points and when I explained to Marriott the reason for requesting the bill they even tossed 5k points my way for my trouble.
So yes, it does happen...not often but you have to be on top of these things to make sure that you keep everyone in line. You're aleady in contact with Amex so thats the start but I'm confident they'll take care of you as they did myself. BTW, this was all last month so my situation is very recent.
