Actually, your forebearer was never held in a prisoner of war camp. On Jan. 2nd, all of the prisoners were taken by rail to Houston. They were held there until January 22nd when the enlisted men were ordered to be released on parole. They were taken by train to Beaumont, by steamer to Niblett's bluff, and then marched to Alexandria. From Alexandria they were placed on transports to Baton Rouge, where they arrived on February 24th and were turned over under parole to the Federal authorities.

The officers were detained, spent a brief bit of time at the Texas Penitentiary and then moved to Camp Groce. In November 1863 they were transferred to Camp Ford near Tyler Texas until they were paroled in July 1864. A handful of enlisted men who had been wounded were kept with the officers. These were 7 privates and one corporal who were also in the July 22, 1864 exchange from Camp Ford.
Your ancestor was not in that group, so it is presumed that he was in the group that was paroled immediately. I think that I have the early parole list on a roll of microfilm. We are currently converting the roll to PDF format. If you will check back with me in a few months, I will see if I have that list.

For what it is worth there is an excellent history of the 42nd Massachusetts that has been reprinted by the higginson book Company title is "History of the Forty-Second Regiment Infantry Massachusetts Vounteers, 1862,1863,1864" by Sergeant Major Charles P. Bosson [Boston, 1866. Mills, Knight and company] I did not see a reference to your forebearer in the book, but it is a good comprehensive history.

Hope this helped.