I have looked at the records for your Vann. There were 5 records and the last had him with the 9th hospital as an aid. This section was usually with the regimental rear and wagons. The Texas Cavalry Brigade's rear was over run by two raids in July of 1964 and many records were lost and people captured. Since there are no records of prision time I assume he was not captured and made it through the war. You can get a good account by reading Fighting With Ross' Texas Cavalry Brigade, CSA, The Diary of George L. Griscom, Adjutant, 9th Texas Cavalry Regiment, edited by Homer L. Kerr. See Hill Junior College Press, Amazon or Alibris for copies of this book. I obtained a copy through library loan.