I've been experiencing the same problem for years. Someone hacked my feed, and I have O subscribers even though more than a million pageviews. I decided to take out my feedburner from Google. In my experience there is not much you can do. The point here is that I am trated within group in level 1. Why? I asked myself , and came to the conclusion that if I was offered something for free and somebody hacked my account, granted that I do not spend my time answering questions.
The answer to your question as well as mine has to come from Google itself, they know what happened and who broke the security we were offered to allow the wrong doing. I have more than 10 years, whatsoever I am not a System Engineer, had made money at the beginning not anymore, got my adsense hacked etc.
All the Best,
Fernando