There are a kazillion ways to use mass media for him to be seen. Skyjacking; maybe seen through a window, Publisher's Clearinghouse winner; he can't collect if he refuses the interview -- it's part of the entry form. Arrested as a terrorist due to mistaken identity. Catches a foul ball at the World Series?
There is the coincidental meeting. I ran into a mall for some insignificant reason, while traveling. I was only going to be there a moment and then I was leaving the state. I passed a girl I had dated 3 years earlier. We watched each other go by surprised at the meeting. If not for that one specific minute I'd be married to someone else now.
A psychic? A reluctant psychic; refuses to believe he/she is "receiving images"? A phony psychic that got lucky?
He accidentally dials a number from his past and his voice is recognized?
He could get rear-ended by someone that knows someone that knows someone... My parents had a party and invited some of their friends. My sister had some friends over too. Turns out one of my sisters friends had T-boned one of my mother's friends the year before and the outcome of the litigation was not satisfactory for either of them. They met in our house. That was a fun night.
He vacations at the same resort that the other person does? This same idea would work with a party, a concert, a political lunch.
Someone needs a transplant and HE has to contact the old family.
A chat room encounter turns into a physical meeting. Surprise! I'm your ex-wife!
New jobs. They land jobs at companies that need to do business with each other and turn out to be business contacts.
Only your imagination is holding you back. Be creative.