why the missions got erased?

So this is my problem. A few months I stoped playing Halo Reach because my Gold suscription expired, but now that I wanted to play the campaign with a friend I realized that my character was not using his armor (he was just not using them, I didn’t lost them), in fact when I started the game it treated me like if I were new to it (it showed me the mesagge where Carter says: Welcome to the Noble Team and bla bla bla…). I put to my character his armor again and then I put the campaign, and everything was gone. There was no missions just “Noble Actual”.
I’m not exactly angry about this, more like confused, I’m gonna restart the campaign again (I already had it finished on Legendary both Solo and Co-op) but I just want to know why this happened, is it a bug or what? has anybody experienced this before?.
I want to apologize if I broke any rules or something I don’t really know how this thing of forums works I just thought that coming here was the best place to find an answer.

BTW I just lost my missions, everything else were still normal, DLC, my rank, the armory, my files, my commendations and even my service record were all normal (My service record still shows who many missions I have played, when I finished the game, that I finished it on Legendary, etc.) just the missions are missing. And sorry if I don’t speak very good the english.

Other thing. I checked if this happend to other profiles on the Xbox and no, just mine has this problem, I also tried with other disk and is the same

Most people say to clear the cache on your hard drive.

This happens to a LOT of people, even though it’s never happened to me.

It’s a profile bug. Reach-related data in your profile got corrupted, causing you to lose your Campaign progress.

Xbox LIVE keeps an online backup of your profile. If you recover your profile quickly enough, you may be able to retrieve a backed-up version that still has the data you lost. If you take too long to do that, your damaged Reach data will be backed up, overwriting the good data.

howw do I clear the cache of the Hard Drive?

and about the backup, how can I recover my profile?, I mean, I think the cloud keeps your profile so you don’t have to recover it again, isn’t it?