In the Spring 2011 GCAJournal, page 32, an article by Marty Black shows a no-trap buttplate with the sling swivel and screw still attached and a clip of AP ammo that he personally found allong the Kall Trail, Hurtgen Forset from the Fall, 1944 battles there. You can assume either correctly or incorrectly that the rifle it was attached to was still a gas-trap.
They were ordered to convert them (when and if the found them).