Can I track someone's location with their phone number?

[Veronica Alicia]

You don't say which Country you are in.
I'm in England, and if I had someone's phone (perhaps through http://www.192.com) I would know immediately which area of the Country that person lived by the code number, for example - 01789 is Stratford upon Avon.
I might check the Electoral Roll then for that Town, searching for, say, William Shakespeare. Hopefully, he has registered to vote and appears on the Roll, so I would have his address.
Otherwise, you could try sites like Friends Reunited, Facebook, Twitter, etc., to see if he is registered on there.
You could advertise on sites like http://www.missing-you.net.
I found my own home e-mail address on http://www.123people.com (which was quite a surprise)
Do you know any of his old friends or a pub which he frequented?