I have the feeling the stats server can't keep up with some of mine killing sprees. I've made 1424 kills in 1 hour and 16 minutes and got 1.187.800 points for it. Thats a little bit over 834 per zombie :S
If you started playing in the last two weeks, then you have lost everything. I don't think it's a issue for Fabio to give you your premium account back.