All inventories disappear periodically. Appears to happen without specific causes. This is in single player survivor mode, with a world that was created in an earlier version (don't know exactly which one). After quitting Minecraft and coming back in, all inventories of loaded chunks are empty - personal inventory and chests. Going back in the world to a far away chest, chests retain inventory.
Has happened twice with same world.
Have you at any point downgraded versions?