[thejeff]

As I understand it, that's pretty much impossible. And yes, I do remember it, though not clearly.

I can only think of two ways for it to happen. One definitely works. If he'd gone berserk, he'd go back to the fight. I don't remember your Wyrm having berserk.
The other I'm unsure of. Possibly, if he went unconscious, when he recovered the AI rechecked the route conditions? I know that can turn off berserk, it might do other weirdness.