Is it possible that the state actor was and is known but that it would be politically incorrect or politically damaging to name it? Pakistan perhaps?
I think it very likely that a "state actor" WAS involved, and that the person behind the state action was hanged in Iraq a couple of years back. I think Saddam passed on the very small quantity of highly weaponized anthrax that his labs were able to produce to Al Quaeda, and they used it.
I've always thought that the idea of a US scientist perpetrator was nuts.