Hey Ho...
We just build yesterday some walls, stone posts etc....when i was logged in today, 1 of the builded walls was...well...gone! Simply gone. No Ghost for a "To build" wall or else...it was simply completly dissepeared, and this part of the wall was allready finished building.
And a day Before a Planned wall was moved away from its original position where i placed it when i logged back in, but in this case i didnt think mutch about it because it was still in "planning" state and nothing that i could fix directly.