Mueller question

Right before they find Himmelstoss has joined their unit one of the characters i listing the status of their class and states 'Mueller and three others wounded'. But we saw his boots get passed on to another soldier. Why would he do that if he still had both legs? And is he ever heard about the rest of the film? I know he dies in the novel but in the film he's last seen crawling along the ground in pain after an explosion. Thanks!