While working on the external decorations of Liontower, I had a goblin siege spring up while about a dozen of my dwarves were outside. Figuring they were done for, I drafted them all, bunched them up together and waited for the raiding party. Sure enough, the dwarves run and do battle, poor little recruits that they are
Then out of nowhere, one of the dorfs decides to run away from the battle. He has no wounds at all! So he runs, runs, runs, all around my fortress, to the opposite wall, back south towards the entrance, into the main corridor, and back to safety.
Meanwhile, the rest of the improvised squad gets completely slaughtered.
My fleeing dwarf was the only survivor of the onslaught. He didn't need a drink or any sort of food. I have no clue what pushed him to hightail it and do a lap around my fort.
I made a burial chamber just for him.
He might have been tired. In one of my recent sieges I sent out 2 champions and 1 swordsdwarf to fend off a goblin squad. Easy enough, right? Well turns out I missed a squad that came from the mountains. 1 champion is off doing whatever and the other 2 have to fight on their own, they obliterate the squad but they're a bit tired.
The champion who was doing whatever arrives, sees that there's no need to help out and takes a nap. The second goblin squad attacks him and cuts him to ribbons. So what happens? The swordsdwarf attacks the squad head on and kills 2 gobbos ... the surviving champion is weary and runs away, leaving her ally to die at the hands of goblins.
She didn't go to bed afterwards, not for some time .. so maybe your dorf was just weary from something. Like cutting trees, operating pumps, mining .. and wanted to go "on break" just that since he's a soldier his status doesn't say "on break" it merely says "soldier" and that was that.
I don't see why you're rewarding him though. I punished my champion by stripping her off her weapons, armor and shield and forcing her to duel a captured goblin hammerlord for her place in the fortress. She snapped his elbow and then snapped his neck.
She has been honorably re-assigned to my army!