Fax your BPs and a brief note and include a printed copy of the CC statement you paid for the ticket with (assuming it was not with cash you paid) showing the transaction and ticket number to Delta at 1 404 715 9220. I have had very, very good luck through the years with credits from partner airlines to my DL account amid many quirks such as what you mention above. They do need to see some evidence that a ticket was purchased. IIRC my cc statement has worked before.

I have to ask though...no electronic copy of the ticket? I did not know not having one was even possible anymore.