Hello. There is a bug in the recent snapshot 15w38b. When shift clicking items into a chest, the items would disappear. When it happened to me, the chest was full, and I shift clicked items into the chest from my inventory (I lost a lot of valuable items) and they just vanished. I tried re-logging and restarting minecraft, the items were still not in the chest or inventory or floating around. I talked about it with my friends on the survival server and it happened to them too. My friend was on a horse and right clicked to open a chest to grab some potatoes. When he shift clicked it to his inventory, the potatoes didn't go to his inventory and just vanished. I suppose its a bug with the player inventory and chests.