grammar - Does this double negative make a positive or negative sentence?

Is that sentence saying that you will worry, or that you won't worry?

最初からユニコーンを見つけるくらい大変だって知っていれば心配しないじゃないですか

I'm pretty sure it's saying that you will worry, since she said that a unicorn is something you don't find right before this. But even without knowing that can Japanese people grammatically tell that it is "will worry", or is it implied based on context?

Or is it "won't worry" anyway? The double negative is confusing >.<