2005 R53 passenger-side headlamp:
running light: yes
low beam: no
hi beam: yes

swapped in both new replacement H7 lamps: no change
swapped the left and right 50A lamp fuses: no change

Any suggestions?

There are FOUR bulbs, not two, as a more careful inspection of the headlights when operating both hi and lo beams showed! Duh. (chagrined, but no longer puzzled)

 

I hate it when that happens. I went on vacation out of state for a couple of weeks, and to keep honest teenagers honest (think 'Risky Business') I hid the keys to the car before I left home. Took me a week to find 'em when I got back. Gettin' old sucks...