Update:
After sending AirChina's replies to UA, UA credited the miles to my account.
However, Air China never stopped claiming that "we can't do anything."
Since the miles have been credited, I didn't pursue this matter any further, but I won't risk an Air China flight again. They're idiots.
Originally Posted by
RobOnLI
NH isn't going to know what NH43887xxxx is since half the account number is missing.
Thanks for posting as you reminded me to follow up!

FYI: I put the XXXXX's there because I didn't want to post someone's account number.