I was walking toward the office, and someone came out of the door across the hall from ours, and started walking toward me.
The guy is probably in his 30s. Does not wear glasses (although may have contacts) -- either way it means he has good eyesight. Almost the same height as me. No way he could pretend that he didn't see me.
I looked him square in the eye and, as we got closer, I smiled, raised my eyebrows, and did the "head nod" thing to acknowledge him.
He never batted an eye. Just kept looking down the hallway past my left shoulder.
Next time I think I'll body check him (or whichever semi-oblivious guy I pass) into the wall as I go by.
Do you think they'd admit that they noticed me after that?