I've spent some time trying to find a "new" ancestor in any census before 1870. After a while of using Ancestry.com, I searched for him on the FamilySearch site. An 1850 census reference was located.
It still may not be my person, but it was a "hit" that for some reason did not turn on up on Ancestry. Different sites have their own indexes. If someone cannot be located in one index, determine if other indexes have been created.