Mysterious province happenings

I had a province in a game that lost all buildings (fortress level 3 in the making), plus recruiting office. I also had troops in the region of about 17 (? can't be sure - could have been more). All of a sudden, the province went blank - both in structures and any troops. Nothing reported. There was no attack that I can tell. I don't think this was an enemy spy event - looks like a bug.

Can someone help ID what happened? This was probably 2 days ago now.

Game #: 273997.
Province in question: Kandalakskaya

Thanks!
RedLimey