Libby forgot about that and did specifically recall. His mistake- now he's paying for it. The problem Fitz may have is he has to prove beyond a shadow of a doubt that Libby couldn't possibly forget the info about the twit Wilson over a period of a few days. So Wilson's importance will have to be inflated to justify saying Wilson was memorable.
How does one prove a negative? Well, while trying to prove a negative to a scientist or a debater os one thing, it's quite another to try to prove a negative to a jury. That's a much easier task.
Now if Fitz has to establish a motive - to prove the alleged misstatement was to intentionally deceive the investigators, then how is Fitz to explain what could motivate a man who was not the leaker to perjure himself.
Libby's in deep doo even though there's no underlying crime- perjury is at the core of our justice system. In Clinton's case it wasn't so much the sex as the press claimed, it was the purjury that made Clinton a real prick.
Whatever comes of it it is a step in a process the Libs are pursuing. Libby's not the end goal.
Libby as McCord? Walton as Sirica? I'm betting against it; the jury will be unable to reach a verdict due to defense demonstrating faulty memories of key witnesses, IMO.