Forum:I built a rather large gold castle and when i opened the map again part of it was missing

I was playing today and built a massive castle using almost 1000 gold ore for the bricks and walls, and then when i went back to the map later the last portion i had built was gone, so i lost about 250 gold bricks and 500+ gold wall. when im playing multiplayer (as i was today to build this) does the map only save every so often?