When Mark leaves Charlie to his fate in the ductwork he is shown crawling toward the camera with no sign of the bag of weapons collected earlier. After reaching the remaining survivors, he kicks out the vent cover and enters the room feet first. There is no bag of weapons and he goes immediately to hug Shelley. At no point is any bag shown from the time Mark leaves Charlie until Mark hugs Shelley. The very next scene is Mark going through the bag of weapons showing the group what he found.