The book Johannes Schwalm the Hessian, page 239, lists Johanes Stumpf under File No. 615, Source Code c, Regiment Kny, with no entry under Exchange List. Source Code c indicates that his name appeared only on the list of prisoners from Lancaster received at Philadelphia. He was part of the von Knyphausen Regiment. There is no indication of who he worked for or the location of any work. With no entry on the Lancaster Exchange List I would assume he was not among those prisoners exchanged in 1777 and 1778, and therefore might have left the Hessian side before this time. Hope this is of some help. Doug MacDonald descendant of Nicolaus Henckell