My bet is that the coins where either lost a long time ago or stolen by insiders. Whoever is responsible will probably get away with it though, because they will blame it on "faulty bitcoin code," and the investigators won't know enough to call out the BS.
Don't worry, there will be enough people willing to testify. His fat ass will end up either dead or in prison, no third way for all the lies and, more importantly, for all the damage he's done to this great community with his idiocy. No matter how many great bitcoin companies real professionals build now, everyone would remember one childish idiot with bad php skills who lost 850k coins and then lied and lied and lied, damaging bitcoin even more while trying to save his ass. Sad.
I just wish people who knew what kind of a joke he is would have been more vocal back in 2012. This site was online since 2011, but should have been heavily promoted.
http://www.mtgoxsucks.org/