Forgive me if this has been covered elsewhere, but I haven't been able to find a thread covering this topic:

I had scheduled a trip on short notice, MSP-ORD-BNA on 2/2 with a return the evening of 2/5, on UA. On the return trip, the BNA-ORD flight was delayed such that I knew I would miss my connection to MSP, and UA helpfully put me on the evening NW non-stop to MSP, which was fine with me as I got to MSP three hours early and didn't have to transit ORD in the process. I normally fly NW on this route and credit my miles to my DL account. Since I took the flight, the miles have yet to be credited to either my UA account or my NW account, let alone my DL account (which would be my preference, as they will give me double miles). So my question is, should either UA or NW have credited the miles, and can I still retroactively do so, even to DL?