Dear Mayooon:
A definition of “coincidence”: A sequence of events that although accidental seems to have been planned or arranged
A definition of “synchronicity”: the simultaneous occurrence of events that appear significantly related but have no discernible causal connection.
Seeing the same stranger twice, as you described, reads to me like both a coincidence and a synchronicity: a random occurrence, that although may seem planned or arranged (by a god, perhaps, or some entity of the like), is not or was not planned or arranged. No “causal connection” means nothing and no one caused this occurrence of seeing him twice on the same day. It just so happened, no different than coin flipping and it landing twice on the same side.
anita