Bug? Units retreating from battle vanishing

[Amhazair]

In a current game I'm at war against Pangaea. I had a smallish army set on retreat orders, in case his Gorgon pretender decided to attack the province they were in.

At the end of the turn, a battle occured in that provinces, due to (apparently) a stealthy Pan producing some non-stealthy maenads in that province. As the maenads had no commander they routed, but obviously my army that was set to retreat did so too.

Even though there were several adjecent friendly provinces, non of the units or commanders that retreated appeared in any of them. I also didn't receive a message saying the fleeing commanders 'did not have anywhere to retreat to' but the entire army has disappeared.

I did not see an issue like this mentioned in the bug shortlist (though I might have missed it), although I would have expected behaviour like this to be documented already, after all I wouldn't think stealthing Pans are that uncommon. Anyone else has noticed anything similar?