From Booth's Record of Louisiana Confederate Soldiets we find...

Private P.H. Phelps
Company F
Powers' Cavalry
Found on Roll of Prisoners of War, C. S. A., Paroled at Jackson, Mississippi, May ?, 1865.
Residence: Baton Rouge, La.

I did not find him in the Louisiana Confederate Soldiers Burial Database. I also did not find a pension application for him in either the Texas or Louisiana pension index.

In the past I have seen where some folks were able to learn about their ancestors in Baton Rouge through the records of the Catholic church. If he was Catholic you may try that.

Please give us as much info as you have on him, such as place of birth, spouse's name, name of children etc. Even a small clue can help. Just curious... did he later move to Texas and Possibly the Indian Territory (Oklohoma)?