[thejeff]

I'm not sure why provinces with 2 sites are skipped. Design choice. Efficiency compromise, I'd guess. The more sites found, the less likely there will be more, so it's more efficient to search provinces with less sites. Just like not searching provinces that have been searched at all in a path.

My standard practice is to let the automated searches finish, then go through and mop up anything they skipped.

Provinces can have up to 4 sites. Determined at the beginning of the game. Some can have effects even before they are discovered, scale changes, unrest, etc.