EarthBoundX5

Ok, I am all kinds of pissed right now, so excuse any errors in my typing.... So just about 20 minutes ago I lost all of my co-op save file history and 3 library entries (essentially everything I have done since first playing co-op). I will lay out the steps that occurred prior to this glitch so that 343i or any foolish person can find if this is isolated or a problem with the game. [Prelude Info]: First off, my save file prior to playing co-op online (ie, how it now looks) had all levels completed 'Solo' on 'Normal' with 42/45 'Library' items analysed. I then proceeded to play 'Co-Op' 'Legendary' with a friend over the last week or so. We completed it several hours ago. I had 2 achievements left to complete, so I figured I would do them at this point "on my own". I wanted to get the "He's Unstoppable" achievement, so I was going to have my girlfriend sign in to play the first while I just hung back.... [steps] 1. Turned on Xbox 360, signed in, loaded game, selected HDD save location 2. Turned on 2nd controller, signed in 2nd profile, selected HDD save location 3. Selected Campaign, only saw my profile listed 4. Backed out to main menu, signed off 2nd profile. 5. Selected Campaign, was prompted to sign in, but only 1st controller was active to select the requested "sign in" button, oddly signed in again with same profile on same controller..., asked to select save location, selected HDD. At this point I instantly noticed something was wrong. My previous default level select was 'The Maw', 'Legendary', '4 Skulls On' and at this moment (and from then on) the default showed 'The Pillar of Autumn', 'Normal', '1 Skull On' Mission Select now shows that I have never played 'Co-Op' on any levels, and my library no longer displays the 3 missing entries I analysed while playing Co-Op with my friend. EDIT: Deleted alot of ranting to repost elsewhere...left steps to warn others/allow for people to try to repeat