When James Comey notified Congress on Friday that he had something to add to his earlier testimony, he pulled the same stunt McCarthy used over 60 years ago, when he declared, "I have here in my hand, a list . . ." He couldn’t show it because it was just a prop.
Likewise Comey.
If the pertinent emails he claims the FBI found in an unrelated investigation can't be released to the public today, they don't exist. Simple as that.