No, DeVall's Bluff was not the site of their prison.

DeVall's Bluff was occupied by the Union Army in September 1863 and thus controlled by the Federals from then until the end of war in 1865. So they could not have been held as Prisoners of War by the Confederates at DeVall's Bluff.

Most Union Prisoners of War taken captive in Arkansas were sent to POW Camps in Texas. The most famous camp being Camp Ford at Tyler, Texas.