I've done this too. Same cunt, every day, though. Just appears on particular streets, out of the corner of my eye. I clock him - He clocks me - The we just stare at each other whilst accelerating harder and harder and harder, all the while keeping exactly abreast of each other, not giving an inch, and still staring into each others eyes.
I turn my head, and then he's gone. Not ahead of me, not behind me, and no longer at my side.
:)
reflection ?