You've picked out a tough one here. Maybe there could have been a staff officer who had antebellum service on the frontier, but it's going to take some time and hard work to find anyone matching your description. Better pack a good lunch!

Not counting U.S.C.T. units, the State of Texas furnished one full regiment for U.S. service, the 1st Texas (U.S.) Cavalry. A second regiment formed but was merged into the first for lack of numbers.