a) Because when I suspect my employer of illegal wrong doing doing I always write an email? Oh, wait, no, we're trained that those sorts of inquiries are supposed to go through channels without permanent records for legal liability reasons. You can argue that that's a bad thing, but that's reality in a LOT of places.
Snowden said he wrote emails that he can't produce despite taking almost two million documents. You can't explain that away since you are directly challenging him.
b) While I'm sure he'd have been capable of snagging his email, maybe it simply didn't occur to him.
And yet it occurred to him to steal documents on intelligence operations by Canada, Australia, New Zealand, Great Britain, Sweden, and other places? All this while intending to make the claim that he was a "whistle blower" on the US? And he forget the whistle he claims to have blown, repeatedly, while there? That doesn't wash.
If your argument is that Snowden didn't keep and release them because they would contradict and harm his 'narrative', then why is the NSA not bending over backwards to get them out there?
Maybe because they don't exist? Or they discuss classified programs that are still classified?
The NSA should be happy to provide us with such a relevant record that details their dutiful adherence to the law, and how they conscientiously explained to Snowden why he was mistaken in raising concerns.
I expect that the NSA has done that in the proper forums for discussing classified matters: in meetings with the administration, in closed sessions of Congress, and before the courts in closed hearings.
And if you really believe what what the NSA was doing was legal, how do you reconcile that with the general consensus that a great deal of what they were doing was not, in fact, legal.
Which "general consensus" is that? The one on Slashdot? Do you really need me to answer that for you?