I was able to add my MileagePlus # by calling Air China. The airline CSR could pull up the full details (with correct name etc) as soon as I read back the 13-digit eticket number. So that is a promising sign.

Just don't stealth-cancel it, please!

Purchase went on a JP Morgan Ritz-Carlton card, so I assume I will have a solid team behind me if I need to chargeback or make a travel insurance claim...not that being stuck in Beijing while it gets sorted is my idea of fun...