General Trudeau was captured 10-24-1863 at Washington, LA. He was paroled 11-5-63 in New Orleans, to remain on the Bringier family's plantation (Houmas) in Ascension Parish. It appears that he broke his parole--the OR contains a letter of his to Pres. Davis in 1864 reporting on conditions in MS. See Arthur, "Old Families of Louisiana"; Edmunds, "Yankees in Acadiana"; Trudeau's CSR.
His actions after Shiloh are not clear. What is clear is that on 9-21-1863 he asked to be appointed Brigadier General PACS, so it is evident he was hoping to get back into the war in an official capacity.
What is your interest in Gen. Trudeau?