Thats interesting.. Did you had any system crash recently? Or maybe disk full? The only moment I think this is the only way to loose object like this. Anyway,

Thats interesting.. Did you had any system crash recently? Or maybe disk full? The only moment I think this is the only way to loose object like this. Anyway, If this is your only repo containing those branches then its gone. The only way you can try is to clone fresh repo from trusted source and then reconstruct every branch manually, basically squashing commits. And I bet, one of those branches will be broken.