No logs, I’m afraid, since I re-loaded BB from its icon and then closed it again without loading up a save, but the latest log was then just a record of me opening and closing the start menu in the last few minutes.
The bug obviously isn’t something that routinely happens under the given circumstances. I simply accepted a contract to raze a goblin camp, with no time restrictions, and after a satisfying triumph (only one scale-clad Level 11 veteran punctured to death by an overwhelmed ambusher who had a height disadvantage) I headed back towards the settlement but the contract panel had disappeared from the top-right side of the screen and there was no reward upon reaching the settlement.
Not sure if anything unusual happened to facilitate the bug. Some goblin wolfriders ran away as I was approaching the camp, and I couldn’t be bothered to chase them. Maybe they were part of the camp and the goblins were not regarded as being fully slaughtered after the battle? But then (presumably) the contract would have still appeared as pending completion?
Oh, but it’s possible it wasn’t a bug at all and that I simply negotiated the terms of the contract and then rushed off to battle without remembering to actually accept it …