No shit eh? even if he did get a minor staff variant that slipped through his lymphatic cycle from scar tissue or some such he still should have taken the anti-bio's. All you're doing by toughing out a minor staff virus that your body can get a hold of over time is helping the virus evolve to become more bad ass. Next time he cops that infection or spreads it through blood on a bar it could be unaffected by common restorative means.
There are so many variations of staff. all day everyday your system finds and destroys staff and other little nasties that live inside you or get inside you. It's the ones that find breeding places safely away from the lymphatic system that get noticeable and need to be treated. scar tissue such as broken noses and such are great places for them to hide.
My old MMA thai boxing coach got one on his shin because his scar tissue build up had separated his lymphatic system from some of his epidermal layer and the virus bred there. He was walking around with his hospital IV stand for a week or more. He hung the IV bag from his car mirror when driving. Funny for us, highly annoying for him.