Bug on 14w02b: All my items are gone

Hallo Mojang,

I lost all the content of the chest, inventory and furnaces. This is how it happened:
I was playing minecraft snapshot 14w04a and
went in to my world.
Then I logged out and
went back to 1.7.4. and
went in to my world again.

All my items are gone from my inventory and my chest's! Could you tell me if it can be fixed, and how?

thanks

Wessel