Not sure what to think/how to feel about this--1st sighting in 15 months

Any advice/stories to share on the following? I am not sure what to think, how to feel; I just know right now I am feeling a bit unsteady, unsettled with what happened earlier today.

As a matter of background, I was viciously D&D'ed by the N in 12/2011, learning from his cell phone and email of the 20+ affairs he was carrying on both locally and internationally throughout our 5-year relationship. I have had no contact with him since 12/2011, but have inadvertently heard things about him from random people in our small community.

My company recently relocated to a new office space in town. I doubt that the N knows this, and even if he did, he probably doesn't know where in this large 3-story building, I sit.

So today, while on the phone with a client, I happened to look out of my 3rd-story window. As I did, the N drove by after he got off from work (my office is en route for him on his way home). I saw the side of his face for the first time in 15 months. It stunned me. The first thoughts racing through my mind were those things that I had heard from random people in my community (i.e., that the N had been traveling. Translation: N was carrying on affairs abroad and having sex with cheap, easy women half his age (believe me, they are cheap and easy)). I felt so unsettled--on one hand, this was the face of the man I loved and missed dearly, and on the other hand, here was this lying sack of perverted, alcoholic shit driving by. Although I could not see him up close, I could nevertheless observe from a distance, that he appeared unchanged, which I was/am rather disappointed about, as I was hoping that life would catch up with him and that he would become disease-ridden as a result of his sexual promiscuity, unemployed (obviously he still has a job b/c he is still commuting), and penniless (it appears that he must still have his home and car).

I don't what to make of this or how to feel; it is so surreal. It will pass, I'm sure, but I feel like the rug's been pulled out from underneath me or that I am teetering on a 3-legged stool. What happens to oneself after the first sighting of a N after not having seen him for many months/years?