Disappearing Stairs

Between saving and exiting the game and getting back on the game, someone sneaks into my house and steals the stairs. There are shadows where the stairs used to be and it doesn't matter what kind of stairs I use (cobblestone, brick, wood, etc.), they vanish and I have to replace them. This only happens in creative mode. And it doesn't affect the stairs I use a pieces of a roof, just pieces that are used as stairs.