All:
There was indeed a temporary American cemetery at Bensheim. According to the unit history of the 46th Quartermaster Graves Registration Company (see
http://www.med-dept.com/unit-histori...ation-company/) the unit scouted the Bensheim site for a cemetery in late March and moved to Bensheim from St. Avold, France on 1 April 1945.
I think it is most likely that the Piper Cub crew investigated the crash and found Lt. Sodermark dead or dying and that he was likely recovered later by a team from the 46th QM Graves Registration Co. and temporarily interred at Bensheim before being moved to St. Avold and ultimately repatriated to the U.S. At his family's request in 1948.
Best regards,
Paul