Do you suppose these people were Creek Indians? Near the bottom of the bio-sketch, you can read about their limited contribution to the Confederacy. They were certainly willing and able, but being only one of two Indian reservations in Texas, they probably never had much chance of being mustered into a unit bound for battle. Their history and relationship with pioneer Texicans is quite remarkable.
https://www.tshaonline.org/handbook/online/articles/bma19