Disappearing items

Put the summary of the bug you're having here

What I expected to happen was...:
De

What actually happened was...:
went into the most resent snap shot than later on i went back to 1.7.4 and all the stuff in my inventory and chest were gone, idk how it happened but it did

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...