Just got smoked in a combat that I *thought* wouldn't happen--was this a bug?

[undead dolphin hacker]

I had a small group of raiding harassers, led by my rainbow pretender, who managed to capture the enemy capitol and were causing chaos in it--I was Blood Hunting and Preaching like mad, generally just screwing up Unrest and such to harm the player while my ally mobilized his main forces.

Pretictably, the player starts moving all his armies toward the captiol province. Knowing I can't win, I order my raiding party to retreat into a province with only 5 or so enemy units, including a commander, in it. The blue line appeared and they were moving--this was a one-movement point action--there was no bold line between the provinces.

Much to my dismay, I get a message next turn saying my sieging forces were utterly defeated by a stronger enemy force! What the hell?! I told them to boogie on outta there! Did all of my armies' soliders spontaneously trip and thus lost their move for that turn, or what?

Note this happened the turn after we all patched--if it had happened in the middle of the game pre-patch or something, I would be a little more inclined to believe I missed some key rule about sieges... but we patched, and the NEXT TURN I get screwed over... makes me think it could be a bug?

(Just for the record, I was playing as Abysia, and was sieging Jotunheim).