Originally Posted by PBIGuy
You'll get credit just the same as if you'd have flown the segments. This has happened to me a few times. Occasionally you can get credit with the other airline, too. It doesn't hurt to try!
Indeed! Last year UA rerouted me on DL CAK-CVG-DSM when my connection through ORD went to pot. I had my US DM number in the reservation. At the DL counter in CAK, they asked me if I had a SkyMiles number to put in the reservation--I did and so I got credit on DL for the flights to DSM. The return on UA was uneventful except for a 3-hour delay at ORD (thunderstorms in July, who'da thunk it?) and the miles posted to US just as they should have. I put in a missing mileage request to UA just to see what would happen, figuring they would credit my US account, and what do you know--they credited my UA account for both the outbound and return as well as awarding me the united.com online booking bonus, which I'm not sure I should have gotten since I booked the trip on united.com on UA metal but with my US DM number. I figure it's just good come-uppance though....since US and UA don't codeshare out of CAK, you can never get one airline's booking bonus for booking a ticket that involves the other, so that 1000 mile bonus made up for past bonuses lost. So in summary, I got both DL and UA credit on the trip out, and both US and UA credit on the way back.
Point is it is certainly possible to get credit on the carrier you were rebooked on as well as US. It is even possible there might be weirdness and extra segments might get credited if someone's asleep at the switch!