Dear Mr. McKenzie,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the Population Schedules for the 1830 Census in the Records of the Bureau of the Census (Record Group 29) but there was no explanation for the missing counties. We also checked NARA’s web site titled Search Census Records Online and Other Resources. We suggest reviewing the 1830 Census, especially sites listed in the Other 1830 Census Resources section, for possible answers.
There may be some mention of the missing countries in the Information about the 1830 Census including the Abstract of the returns of the Fifth Census or the 1830 Census: Fifth Census; or Enumeration of the Inhabitants of the United States on the U.S. Census Bureau website. We also suggest contacting the Census Bureau via the Frequently Asked Questions website.
We hope this is helpful. Best of luck with your research!
Appreciate you looking at this....
Guess it's a mystery yet to be solved. The records must have made their way to D.C. as the aggregate numbers for those 'missing' counties are included in the 1830 reports