Since there is no publicly available wireless number database, try searching for the cell phone number on Whitepages.com. The website collates information from directories and from third party data providers who may have gotten personal information from contests, sweepstakes and other forms filled out by consumers.
Calling Directory Assistance may also provide cell phone numbers; however, its database only contains information on the customers who allow access to their data. A Directory Assistance charge is billed for retrieving directory information.
Facebook can be used for cell phone number lookup, People with public profiles may have their cell phone numbers displayed on their accounts. Reverse lookup to identify an unregistered number is done by searching using the cell phone number.