Greg,
That's kinda what I figured. Either that or something similar to the 6th Texas or 17th Texas flags. (Red field w/ blue device [one shield, the other circle] with a circle of stars) I'm pretty sure that after they were paroled and transfered to Cleburne's Div., Granbury's Brig., they carried a flag similar to the 6th & 15th Consolidated or 17th & 18th Consolidated.