Why did my stats reset to 0?

I've had 5 days worth of gameplay last night, and all diamond guns. I come online today, and it's like I've just started the game for the first time.

I've never boosted, used glitches or any cheats, and I'm pretty pissed about the fact that I have to start from the beginning again.

Does anyone have any idea why this might have happened? I've had pretty decent K/D Ratios the past few days, sometimes up to 40+ kills and only 1 death, could this be why?