I booted Halo 4 up today to get the lone wolf achievment. I already beat the first 6 missions. When I wanted to select the next mission, my campaign progress was gone. I couldn’t even select the missions I have beaten before. Is there any way to restore my campaign progress? I won’t play through the whole campaign again on legendary alone. If there is no solution Halo 4 will be the only Halo game where I didn’t get every achievment.
Are you signed into Xbox LIVE when you play Halo 4? Were you signed into LIVE when you were playing the campaign and getting the achievements for it?
Hi yes I was signed in when I got the other achievments and I was also signed in when I wanted to continue the campaign today
It’s done this multiple times to me. And as far as I know there is no solution. 
Sadly there is no way to restore your progress other than replaying the Campaign.
Did you quit the end of a match while the game is “saving status”?
This issue began occurring as a result of the Champions Bundle TU in August 2013. It was then resolved in a TU in November 2013. There is no way to restore your progress, but it should only happen to you once.
That sucks
As The Little Moa said, it seems that you’re going to have to replay the campaign again. I know of many who ran into the same issue and I have as well, my campaign progress was completely wiped.