Hello!
We're terribly sorry, but that's definitely a bug. The fight is supposed to restart from the beginning cutscene with no QTE active.
The lack of a defeat scene, on the other hand, isn't a bug. There simply isn't one for this particular boss fight.
If you load an earlier save, you should be able to get through this part just fine. We haven't received any other reports about this specific fight, so it might be a rare case of the event bugging out.
Just for the sake of fixing it in a future version, do you remember doing anything unusual that might have caused it? Based on various reports, we've found that the game can sometimes act up when someone uses Mtool to play it, due to the way our events are structured.
Again, we're very sorry for the inconvenience and we hope you'll be able to enjoy the rest of the game in peace. ^^