Mods: feel free to merge if there is a thread specifically addressing this question. I searched but did not find one.

I just happened to check on two upcoming trips. Both were booked while I was logged in as a 1K. Both itineraries contain info from my (1K) profile — for example KTN and traveler contact information — but I suddenly noticed that both itineraries had me listed as a United non-member. That would have meant zero earnings if I hadn't picked it up. I clicked on the link to Add frequent flyer program and manually added my MP number, and my status now seems to be displaying correctly along with the last three digits of my MP number.

How does it happen that one's status "falls out" of a reservation? Is this a known glitch? Should everyone be checking for the same thing?