I have in the past found some apparently missing people who disappeared from Georgia and reappeared in Mississippi two or three decades later by looking in Alabama. I tried the names Isaac and Nancy Milner under various spellings of Milner in Alabama in the 1850 census index with no useful results. They could have been missed in any of the three jurisdictions or in the Carolinas or Tennessee for that matter, or the census taker could have been more creative with the spelling than I have imagined. They could also have been missed by the indexer. I regret that I can be of no more help with this. I do believe that the Harris Co. marriage record heretofore mentioned applies to this family.