Lindsay Sapp shows up on the muster lists of Company B, 3rd Missouri State Militia Cavalry (New). This unit was unrelated to the 3rd Missouri Cavalry. Also unrelated to the 3rd M.S.M. Cavalry (Old). The bad news is the rare book relating to the 3rd Mo. Cav. will be of no use for your purposes.

A number of Pike County Ill. men crossed the river and joined the 3rd M.S.M. (New), which mustered in out of Louisiana, Pike County, Missouri. Company B consisted of almost 100% Illinois men. Around 1/3 of Co. E and 1/2 of Co. I consisted of Pike Illinois men.

I am currently writing a book on the 3rd M.S.M. (New) and may be able to answer more questions on this unit at CivilWar@missouri.usa.com