Breaking a chest filled with blocks or items in creative with a full inventory will result in the blocks from the chest being picked up, however the items will not appear in your inventory, even if you empty out some slots after you break the chest. (works with all types of chests, and it dosen't matter how many stacks of items/blocks you put in the chest)

This bug also happens when dropping items on the ground, and quickly filling up your inventory with items.