Surmising a brief sum up.

a) Only one transaction gets registered in the blockchain -> no blockchain-based autopsy is possible.

b) There have been some  interesting contributions discussing the Gox software. I wonder whether it is available and can be inspected. Perhaps it would be reasonable to require exchanges to make their software available to public scrutiny. If a chunk of the Bitcoin ecosystem is a black hole it's hardly surprising that it swallows money.