Well if by chance you do bump into him again, then ask for a phone number, an email address etc. so you can keep contact with him. But this is just chance. Ask your friend if he knows anything about him, which may aid in finding him (if he was to work in a particular shop then you may find him there).
The age difference is nothing to worry about, there are many who find it stupid for a bigger age gap, but it still works (it has been known for relationships with a 20 year age gap to work well).
Now hoping you do see this person again and do get contact details, then just talk more, take it easy and slowly. You don't want to rush in (which can cause big problems in the future).