Yes, I have the prison ledger entry for Thomas R. Pennington that I obtained from Joanne Eakins' 1975 work "MO POWs" taken from the National Archive records. It says:

Civilian Thomas R. Pennington of Polk County was captured or arrested in Polk County 3 Sept 1862, sent to G & M [either Gratiot Street or Myrtle Street Military Prison, both in downtown St.Louis), from which he was sent to City Point [place where prisoners of both sides were exchanged in VA] as of 2 Jun 1863.

That is all it says. Why was Pennington captured in Polk County 3 September 1862? Don't know, but throughout August 1862 the Confederacy put on a large-scale recruiting drive hundreds of miles behind Union lines in western MO. Some of this recruiting took place in Polk and surrounding counties. My guess is that Union troops captured recruit Pennington, and called him a civilian because both he and they were unsure of his actual military status at the time of his capture.

That's the best I can do with this. I hope it helps.

Bruce Nichols