How can you prove there isn't a way to prove a negative? ... Good one.

But your argument doesn't mean the argument isn't sound, it just means that we shouldn't believe something just because we cannot disprove it.

Penn Jillette puts it wonderfully when he says that atheism and agnosticism are answers to two different question. Agnosticism is the answer to the question: "does a god exist?". Atheism is the answer to the question: "do you believe god exists?".