Originally posted by bladder:

I've spent a couple of hours roaming around some unexplored plains on my dedicated server running a pre-H&H seed, and I've not found one yet. My server is running the patch that came out today.
Am I just unlucky?

did you read the latest patch notes from today?

by unexplored they need to be 500m+ away from anywhere a player has been before, which is quite a bit further than the unexplored fog on the map. For reference the base zoom for the minimap is somewhere around 100-200m range.

If you uncovered your map, or explored the plains too much while waiting for HnH you might be out of luck on that world. New areas won't update on parts of the map you've been to, and tar pits spawn 500M away from where your fog of war ends in plains biomes.