This scenario happened to me, but slightly different. I upgraded my ticket to D1 and received the charge as pending on my Amex. The charge then dropped off today. I called Amex and they said that Delta needed to issue a finalized receipt to make the charge go through. So I then called Delta and the wonderful agent at the PM desk called ticketing support. They all said that the ticket looked good on their end and there is an approval code for the charge. In all likelihood, it will reappear on my statement at some point soon.