I was idly playing with Google Maps a moment ago and zoomed into the Gregerson's house at Namwianga Mission in Zambia (just south of Kalomo) and was surprised to see that their house had been removed as if by a knife scrape on a film emulsion. I'm sure that's the place. I recognize their yard and their garden across the road. It's just another quirk of the global mapping database. I suppose it could be a sunflare from their metal roof or even some kind of crude security mask, but I suspect it's just an accidental injury to an aerial photo or something like that.
Update: The more I look at it the more it does look like a sun flare.