What was posted above just happened to me. I was downloading The Walking Dead arcade game. My characters were all at MAX level. I went to play survival mode and after I went back to the lobby, survival and the other unlocked mode were no longer there. Also gone were my maxed out characters and all the levels I passed. Now I have to run through the damn game again just to play the survival modes.
My advice is to back up a save to a memory card or flashdrive. You dont want to lose hours of gameplay in a matter of seconds like I did.