A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,417
AFAIK there's no requirement that the ticket be paid with a DL AmEx card, so for example tickets purchased by corporate travel offices do get the bag fee waiver.
Your DL AmEx Gold card should be attached to your DL FF account. It probably should show (but not the number) when you log into your account. If this is done right, the bag drop place (or the OLCI page where you specify the number of bags you plan to check and delta.dumb shows the fees) should immediately see that you have a Gold DL AmEx and qualify for the fee waiver.