ok...b/c no OP is ever 100% honest about their situation, i'll come clean:
about 2 weeks ago I did spend about 1.5hrs deleting past tickets while sitting on a sfo/pvg flight. Figured that would cure the issue. Today, on pdx/den/dca journey, the pdx/den ticket showed on home page...but upon boarding in den, the den/dca ticket wouldn't show until i found it in wallet attached to pvg/sfo return flight.

It could be a memory issue, altho I would have hoped that by cleaning out 98% of old tickets I'd have been in the clear.