I had some bad luck recently flying in and out of LGA.

10/10 ORD-LGA on UA 680, 733 went mechanical and I was put on 682 by the RCC agent. I boarded and sat in 6A, after a few minutes of boarding someone tried to sit in 6A, we both had boarding passes for 6A. .bomb shows that it was re-booked into the Y fare bucket, which I was happy about for the bonus EQM's, however, when I try and apply for missing millage credit it tells me I didn't take this flight. The gate agent came on board and collected both of our boarding passes, they "cleared" it up and sat the other person in the back of the plane. I never got a boarding pass back even though I asked for one.

10/14 LGA-ORD on UA 685, 735 went mechanical and I was put on 689 by the gate agent. This time it was re-booked into the W class, and I do have the boarding stub from this flight.

How should I go about getting flight credit for these, especially important since I am in a 1P challenge right now.

Thanks for the help!