This is a user support forum for church technology, so it's unlikely anyone here will be able to help.
In you case I'd try searching for him on Facebook, LinkedIn etc.
If you can remember the area where he lived, you could look up the ward where he currently is on the meetinghouse locater (
https://www.churchofjesuschrist.org/maps/meetinghouses/ ), and send a message to the local Bishop. Privacy rules will stop him passing along the person's info if they are still there, but he could pass along your info to the person.