That's tough, especially if you didn't expect to see what you saw. I think the others are right - it doesn't necessarily mean that he's moved on to a beautiful new relationship; it is more likely to mean that some other woman is now going to be stuck with the same craziness that you have opted out of.
I recall exactly where I was some years ago (international departures area of the Colorado airport, if you want to be precise), when I learned my ex was dating someone new, who went on to become his second ex-wife. That ... didn't work out very well. But at the time I felt it like a punch - especially because I was nowhere near ready to start dating again and was convinced I was going to spend the rest of my adult life as a crazy cat lady.