deleted all inventory and chest items when switching from snapshot to 1.7.4

Put the summary of the bug you're having here

What I expected to happen was...:
I expected to just be able to switch to the previously released version (that was not a snapshot)

What actually happened was...:
When switching I lost all of my items. All of my items inside my inventory and all of my items in my chests were gone

Steps to Reproduce:
1. (before the switch) I had lapus and a book and was trying to enchant the book, I had entered the items into the enchanting table but never actually enchanted anything yet, then took them out
2. I switched from the snapshot I was in to 1.7.4
3. opening minecraft back up in 1.7.4
4. all inventory and chest items lost
5. after realization of everything i had lost items I switched back to the snapshot and items are still missing...