I have been working on Lone Wolf Legend and after finishing some missions today I saw ever mission besides the three I finsihed today are locked or gone. I just finished Requiem, and Shutdwon. I am on Composer right now. Anyone know why this happens and if I can get my data back.
Well on your Campaign progress stats it says you’ve finished all the missions Legendary Solo, so I’m not sure, it should still count.
it happened to me before as well… just make sure you’re online when you’re playing otherwise it won’t count… since it has to connect to waypoint as well .
Good luck 
It happened to me as well, waypoint shows the correct achievement but your access to individual levels on your xbox is gone - its a game bug - some sort of failed sync between the stored game profile on the xbox and the waypoint server. Anyway its been like this since release - but 343 are busy fixing bugs no one cares about or even heard of.
The same thing happened to me a while back.
I’m sorry to say there’s nothing you can do about it.
Or at least, I couldn’t find any solutions searching on line.
I just had a discussion the other day in relation to vanishing campaigns. Also, check to see if you’re missing any terminals.
Sadly there is no fix. The least you can do is to call Xbox Support and tell them the issue; the guy I talked to experienced the problem as well! It can be tedious going through the process, but this could help in getting this problem some much needed attention; plus you might get a little something for your troubles.