Sorry, I was incorrect, it turns out they raised $1 billion, most of which went to the existing investors.
Of course, reasonable people can disagree on this, but I think the questionable accounting standards (see: adjusted consolidated segment operating income) that they made up to hide their huge weaknesses before the IPO came straight from the top.
I think Mason knew the wheels were coming off even before the Google offer, and he decided to take the guaranteed 1 billion instead of risking not making it through due diligence with Google. Then, push the accelerator to the floor, try to obfuscate the numbers as much as possible, and get away with as much money as possible before the IPO investors were left holding the bag.