Materials about how to locate missing persons are classed in the Social Sciences Collection. Note that all materials are published for the U.S. market and therefore discuss American government departments, lists and legislation; there are no materials specifically written for the Canadian market at this point in time. However, the techniques and concepts described could be useful. Try one of the following subject headings:
The Salvation Army operates a service to help people locate family members with whom they have lost contact. More information is available on the Salvation Army's Family Tracing page.
Cyndi's List provides a set of Finding Living People links to resources for finding people.