I've got an orbitz booked DL itinerary coming up at the end of January. Once I hit the 90 day time frame I called the DL diamond line and got assigned KL EC (or whatever they call it) seating for the two transatlantic flights. A few weeks later the return schedule changed and I called again and got rebooked from KL on the return to DL AMS-DTW. Again straight into EC.
At that point the entire itinerary disappeared on DL although it was still there on the KL www site with the KL PNR that I'd gotten from an agent.
A recent email to talk to us resurfaced the itin on delta.com, seats still in tact but with a new ticket number. Seems they reissued the ticket but didn't change the PNR when the fixed the schedule change. Needless to say, I'm watching the trip closely.