Here’s one that’s providing check marks for the right boxes.
11th Kansas Infantry/11th Kansas Cavalry. Duty on the Kansas/Missouri border. Led by Radical Thomas Ewing. Did duty at Fort Leavenworth. Converted from infantry to cavalry at Kansas City in 1863.
In Company E I find a 1st Lieutenant Charles Drake who had a Thomas Smith in his command. This Thomas Smith later ended up in Company L/19th Kansas Cavalry which was a postwar/1868 Fort Hays Indian fighting 6 month militia unit.
So, maybe, incapacitated by disease late 1863. Recovers, western Missouri not a hospitable place for somebody who served under Ewing (Order No. 11) heads back for postwar duty on the Western Kansas prairie, afterwards ultimately makes his way out to California.