Finding missing persons

The Social Security Administration is there to help:

We will attempt to forward a letter to a missing person under circumstances involving a matter of great importance, such as a death or serious illness in the missing person's immediate family, or a sizeable amount of money that is due the missing person. Also, the circumstances must concern a matter about which the missing person is unaware and would undoubtedly want to be informed.

There is no charge for forwarding letters that have a humanitarian purpose. However, we must charge a $25 (effective July 1, 2001) fee to cover our costs when the letter is to inform the missing person of money or property due him or her. This fee is not refundable. The fee should be paid by a check that is made payable to the Social Security Administration.

You will need to have some information:

To try to locate an address in our records, we need the missing person's Social Security number or identifying information to help us find the number. The identifying information needed is the person's date and place of birth, the father's name, and the mother's full birth name.

Read more at the Social Security Administration linked here.