What was the dirigible battle about?

I just left a location in the Moors, and was instantly attacked by some dudes on a dirigible when I was in a bad condition to fight. I lost very quickly and want to get revenge, but now I can't find them. It seemed like they were just flying around the location, and if I was nearby, they would have flown closer to me and attacked, but it all happened too fast, so I'm not sure.

The middle guy in the trio said at the start of the battle: "I've just killed ten like you" or similar. Not sure if it's a common battle starter phrase or a unique one. But the dirigible battle background I've never seen anywhere else.

From the information I have found here it seems that the airships will spawn once you've completed the Junktown dungeon. Then if you defeat enough of these and after you've completed the Crimson Garden dungeon a boss has a change of spawning.

This boss is called High Captain Blothe and will give you a lot of XP and the achievement "No Parley".