Going through a list of Thomas K Smiths I find the Hawkins Commision report on Johnson's Independent Company, Caldwell Co Home Guards which lists Thomas K Smith, 1st Sargent of Mirabelle MO enlisting June 18, 1861 and discharged Sept 3, 1861, due $59.52 paid May 28, 1864.

1850, 1860, census with parents family in Caldwell County, married Hattie C Smalley 8 Aug 1866, Caldwell County. 1870 with wife, son George Palmer, and parents in Cameron, Clinton Co MO. Listed as physician. 1880 has him in Cameron with wife Hattie and son George Palmer but occupation listed as Boot and Shoe Merchant. 1900 finds him with wife and second son Eugene in San Diego CA as a physician.

Directory of Physicians has him graduating University of Michigan 1867 dead at La Jolla CA Aug 8, 1908. California physician license issued Aug 16 1897 with med school University of Michigan graduating Mar 27, 1867, school records listing Mirabelle MO as home. At the time medical school lasted a minimum of 6 months so presumably he went to med school shortly after his marriage in Aug 1866.

So the only real war gap is from his July 1863 draft registration to August 1866.