I not 100% sure if theres anything that anyone can do the game saves are set to your profile so even if someone had one to give you I doubt they'd work. Whenever my xbox plays up & randomley signs my out it kicks me out of my game saying that the gamer tag has changed & that the game is nolonger available untill the gamertag is signed in again. Same go's for the other gamer tags I have on my xbox, I can't play games assigned to another acount.
Unless someone else hear can tell you a way around it then the only thing I can tell you is that you'll have to start again. If your gamertag itself is corrupt then you'll have to contact microsoft customer support to see what they can do otherwise you might have to create another profile. Sorry I can't be of more help.
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