Paintings and Item Frames disappear.

Put the summary of the bug you're having here

What I expected to happen was...:
When i put the Item Frames/Paintings down i thought they would stay.

What actually happened was...:
Once i left the chunks and came back after a while the Item Frames/Paintings weren't there anymore.

Steps to Reproduce:
1. Place Item Frame/Painting.
2. Leave the Chunk and come back Later.
2. Item Frame/Painting Was not there anymore.