One day, you will see him and think he is sort of familiar, then a while later you may walk right on past him, because he will be just "a face in the crowd".
Til then he's an ex, that means he ain't yours no more, someone else is stuck with him, and whether he's doing handstands on the boss's desk or doing a Tarzan, swinging thru the office by the light cords, it doesn't change the fact that he is still no longer your problem, your reason for shame, anger, sorrow or grief or whatever.
God bless