Found this. So your certificate number is still your SSN, as it sounds like you never completed the form to request a change.
FAA To Stop Using SSNs as Pilot Certificate Numbers on June 1
May 8, 2002 - Recent security and identity theft concerns have led the FAA to cease its policy of using Social Security Numbers (SSN) as airmen certificate numbers. Effective June 1, 2002, all original airman certificates will be issued by the Airman Certification Branch (AFS-760) with unique certificate numbers. Pilots with existing SSN certificate numbers can complete a form and have the FAA assign them a unique certificate number. Through June 1, new Airman Certificates will continue to be issued using the SSN unless the airman requests a unique number. FAA’s
Request For Change of Certificate Number form is available for download at
http://registry.faa.gov/docs/SSN_Change.pdf.