My skulls Disappeared in halo 3 and i lost the unlocked stuff, what gives?

[The Question]

I created a new king of hill game and for some reason it wouldn't give any points, so my bro saved it then after going to the harddrive to check it out my save data got deleted. What could have happened?
Does anyone know why this happened?

 

[mypetrock!!!]

Basically it means your screwed... sorry.