Put the summary of the bug you're having here

Upon Shutting down computer the world save folder's DIM1 file loses contained files 

What I expected to happen was:

My computer was lagging out and I had decided to shut it down by using the power button as it was not letting me open the start menu.

What actually happened was...:

The computer restarted and the open applications were closed.  I relaunched minecraft only to find that my world has vanished.  I discovered that the DIM1 folder had lost the poi folder. This has occurred before and at that time DIM1 lost both poi and region folders.

Steps to Reproduce:
1. Open a world and perform actions
2.save and quit world 
3. While in world menu, use power button to force shut down the computer.

4. The world doesn't appear on relaunching game