My Mule Dissaperad with all my goddies.

I like to use a mule to carry extra stuff, but I must make sure there's a clear path for him to travel. When I returned to my secure area where I kept him, the mule was gone with all my stuff and a spider was there instead which should not have been possible. Is there any way to get it all back? Can you please create true "Save Games" for Mine-craft?

Much Thanks: TerBear: <;}}><