He wouldn't have if he did it right. Security was very lax if you've followed anything about the situation. Whereas, I've done exactly this in a higher security setting. I'm not speculating.

He can bug his computer. He can hide executables tgat copy it to disks. He can screenshot it to disks. He can photo/video the screen. Examples abound. And remember he's a trained, ex-CIA spy. Not some idiot that cant pull off fieldcraft 101.

He just failed to collect evidence one way or another for a key claim.