I was playing vanilla 1.8, and because of excessive lag/low fps, decided to change the version back to 1.7.10. Expecting to have a smooth transition and keep all my items etc.

I quit out of the game and switched the version, when i started the world i was playing, my hot bar was empty. I checked one of my chests nearby for an axe and found that it was empty along with my inventory. I proceeded to my nearest base and found that all chests in the loaded chunks were empty. However all chunks that didn't load retained all items. Switched version again back to 1.8 and missing items remained missing.

Steps:
1. open inventory in vanilla 1.8
2. 'x' out of window without 'save and quit'
3. change version to 1.7.10
4. upon reload chests and inventory within loaded chunks should be empty, nearby item frames and paintings should be knocked off the wall they're on.

The included game output log starts after i loaded 1.7.10 and switched back to 1.8