As a prisoner of war, he may have been given a choice to remain in captivity, or be released on taking the oath to the U. S., whereupon he would be released and allowed to remain at large as long as he did not take arms up against the U. S.

By agreement between the armies men were paroled and released on honor that they would not take up arms again until exchanged. This was a formal agreement that the two foes would take up naming regiments so involved.

Capt. Jack Waterhouse commanded Company I of Lane's regiment. From the records I do not find a Company K, L, or M in Lane's cavalry.

...

1st Regiment Partisan Rangers was formed during the summer of 1862 with about 1,000 men. Many were from San Augustine and Paris. The unit served in D. H. Cooper's, Major's, and Hardeman's Brigade in the Trans-Mississippi Department. It fought at Prairie Grove, skirmished in Louisiana, and fought in the conflicts at Mansfield and Pleasant Hill. Later it continued the fight in Louisiana and in May, 1865, disbanded. The field officers were Colonel Walter P. Lane, Lieutenant Colonel R. P. Crump, and Majors A. D. Burns and W.P. Saufley.

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Gano returned to Texas in 1863. Per the ORs, he was transfered to the District of the Indian Territory under Gen Wm Steele and given command of what was Bankhead's Brigade which was located at Camp Hardeman in the Choctaw Nation a few miles south-southwest of Ft Smith AR (I believe on Sugar Loaf Creek -- Cooper's camp was named "Camp Sugar Loaf). Gano arrived there on Nov. 1st "with a company of men" presumed to his Grapevine Guards. His brigade was ordered back to the Red River to be supplied/clothed for the winter.

Gano’s Brigade Summer 1863 on

29th Texas Cav.
30th Texas Cav.
1st Regiment Arizona Brigade
5th Texas Partisan Rangers
33rd Texas Cavalry
Welch’s Texas Cavalry Company
Well’s Texas Battalion