That Johns Hopkins study in which John R. White is mentioned was adapted by its author, Harrison A. Trexler, into a January 1914 Missouri Historical Review article, and also mentions White. Both versions document in some detail that Missouri slave dealers generally were outcasts lower on the societal spectrum than saloon-keepers. So I suppose that despite being one of Little Dixie's most prominent landowners and agricultural producers it's possible the newspapers stayed away from mention of him for that reason. Also, while the Department of the Missouri Provost Marshal's in-depth early 1864 investigation into the Order of American Knights mentioned him and his son Oscar as being members of that secret society, there doesn't appear to have been a concerted round up of the people named. In fact, that report actually asterisks the ones who were under arrest, under oath, and/or under bond. And the Whites were none, at least by June 1864. So that could account for the Whites not seeming to appear in local provost marshal reports or Gratiot and Myrtle Street prisoner intake reports (so far as I can see).