I had a similar situation ORD-MKE on 3/2...
Booked two ow tix SFO-EWR-ORD-MKE and MKE-IAH-SFO and upon arrival at ORD, I receive a text from United saying my MKE-IAH flight is delayed 3 hours which will cause me to misconx at IAH so I go to to the service desk and the agent recommends walking alway from the ORD-MKE segment and re-booking me ORD-IAH to catch my original IAH-SFO segment.
3/3: Submitted for ORC on line after I returned home to SF where I was told that I would receive ORC but I had to wait 5 days from date of travel and to re-submit at that time.
3/10: Re-submitted as instructed.
3/11: Rec'd and e-mail saying "no, only flights flown unless involuntarily re-routed blah-blah blah"
3/11: E-mailed back saying that it was thru no fault of my own as had I flown as booked, it would have been worse for UA as I would have misconnected plus the change was at the recommendation of UA.
3/11: Rec'd a response stating that difference in qualifying miles was only 117
but as a token of appreciation, 500 redeemable but non-qualifying miles were deposited to my account
3/11: Sent the most dumbed-down spreadsheet showing that the difference was 599 miles not including the "Y" fare bonus for ORD-MKE
3/12: Rec'd a response saying "I'm not sure what you are asking, can you please provide more information"
3/12: Called MP and it was handled in less than 10 minutes^ and that everything should post correctly in 24 hours
(note to self: always call MP for ORC going forward)