I think a different tack happened.
Comey gave this to an assistant to destroy. The assistant either decides he can use it as blackmail or is a patriot and decided to squirrel away.
Kash comes in and either the assistant uses it as leverage to not be fired/jailed or was hoping for this moment.
I honestly believe Comey did not think this evidence was still in existence having told his lackey to destroy it.
😢