On Sunday May 4th, UA 882 NRT-ORD was cancelled and I was re-routed onto UA852 (which had a MX delay) then UA2 to IAH and eventually home to complete the trip. My reservation on .bomb shows the following:

Wed., Dec. 31, 2014 | Tokyo, Japan (NRT - Narita) to Honolulu, HI (HNL)
Depart:
00:00
Wed., Dec. 31, 2014
Tokyo, Japan (NRT - Narita)
Arrive:
00:00
Wed., Dec. 31, 2014
Honolulu, HI (HNL)
Travel Time:
19 hr 0 mn
Distance:
3,818 miles
Flight:ZZ123
Operated by Corporate Aircraft.
Fare Class: Economy (Y)
Meal: None
No Special Meal Offered.
Change Flights View/Change Seats
MileagePlus Members: Upon completion of this itinerary, you will earn up to 3,818 award miles.*

I'm sure this due to the mysteries of .bomb, but it is the weirdest thing - I was hoping UA booked me on a corporate jet to celebrate New Year's in HNL as compensation

This is a retention segment to keep the PNR from expiring. Some old-school agents still do this to keep the PNR history intact - usually when some sort of manual exchange has been done.

Axey nailed it. The PNR disappears about 2 days after the last segment (although it is stored offline, access to it is difficult/restricted.). If an "old school" agent thinks access to it may be needed later, we can add a fictitious flight segment for a far off date to keep the PNR active.

I was using old school in the flattering way. For the record

^^^

Threads like this are what keep the UA forum worth reading these days. Still amazed at the stuff you can learn here.

It'd be fun to show up at the airport and start frantically trying to check in for and find the flight.

I absolutely agree - I also had wondered about these added-on fictitious sectors, and now I know... ^^^

I experienced this before, thank you for explaining!

Thanks for all the replies, like others have said, learn something new everyday!

Had this happen to me as we'll a while back, before I knew FT existed...