Well for me what happened was that early in the fortress, i was invaded by giant 4 Koati's, i drafted my lumberjack to the military, not before making a rigid scaleplate helm and armour though, but what i didn't make was gloves (ran out of scales) so i sent him to the koati's. He killed one....... and then the other one ate his hand.
It was then when he decided to run. That was the first time i ever saw a military dwarf logically logically asses the situation and runaway from a fight he couldn't win. Funnily enough the koati's also ran away.
So after that, i did what any sane dwarf fortress player would do.... i immediately create a fully functional hospital in under 5 minutes. But i had a problem... he wasn't going to the hospital for some reason. I tried googling and disabling all of the doctors other labors. After i finally gave up i pressed z and checked the health tab.
Apparently what happened was that despite missing a hand and still flashing heavily wounded, he stopped bleeding by himself. So what that meant was the reason why nobody was operating on him was because he had already recovered from his injuries.
It was the most incredible thing that happened to me.