I can see where the confusion exists. The 1st Texas Cavalry was sometimes called the 31st Texas Cavalry because of the error in assigning numbers.

Major Looscan took command of the 1st Texas Cavalry or sometimes called the 31 Texas Cavalry duroing the Camden and Poison Springs engagements.

NPS Soldier and Sailors System
Field officers for the "official" 31st Texas Cavalry:
Col. Trezvant C.Hawpe
Col. F.J.Malone
Lt.Col. G.W. Guess
*Maj. Michel Looscan
Maj. William Peak

Field officers for the 1st Texas Cavalry: (Sometimes called the 31st Texas Cavalry by mistake)
Col. Peter C.Hardeman
Lt.Col. Edward Riodan
*Maj.Michael Looscan
Maj. Alexander Terrell

*Maj.Looscan is listed in both regiments. I feel that may have been because of the numerical error and Maj.Looscan was never in Col. Hawpes 31st Texas Cavalry. However, I presume the NPS Service obtains their information from the official muster rolls.

Col. Hawpe resigned the command of the 31st Texas Cavalry and returned to Dallas to manage his freight company. A teamster or owner of a freight company is an occupation that allowed men to be exempt from military service. Soon after he returned to Dallas, Hawpe was murdered by a man he arrested when he was Dallas County sheriff. He was the first elected Dallas County sheriff.