Wooden Door Disappears when Save/Quit and Reload Single Player World

What I expected to happen was...:
In a new single player, survival world, I made a simple wooden house with a wooden door. I left the world (Save/Quit) and then re-entered the world. The wooden door on the house was gone. I expected it to still be there.

What actually happened was...:
The wooden door that I placed on the house disappeared.

Steps to Reproduce:
1. Cut down a oak tree.
2. Break the oak wood up into wood planks.
3. Take 6 oak wood planks to make a oak wood door.
4. Make a 5x5x3 house with the oak planks with an opening for a door.
5. Put the oak door in place.
6. Exit the world (Save/Quit)
7. Re-enter the world.
8. Door will be missing.