My Leader boards are still there but last night Me and my zombie partner failed on round 82 Origins trying to beat our 2 player 85. After the game he noticed all his leaderboards were all erased apart from his global stats, he did not even have the 82 we had just got saved. I read somewhere that it is down to data corruption because if it were a reset then everything including rank, stats and leaderboards would be back to nothing.
My zombie partner is an awesome player and plays legit, he puts more time into zombies more than anyone I know. This is the second time that his leaderboards have corrupted, the first time he managed to get his grief wins and losses back but nothing else, he put the time back in to equal and even beat most of his records. One guy on his friends list also had the leaderboards erased on one of his accounts.