I interpreted the "can't determine when it was downloaded" to mean that the time stamp, file location, or other metadata either implied another user downloaded/copied it, or ruled him out as the downloader. If they were to plant a file, I would think they would match the times stamp, etc., to clearly implicate Gartenlaub (assuming minimal competency, which could be where my expectations diverge from reality).
IANAL, but isn't restraining someone and keeping them in a place against their will without any legal justification also known as kidnapping? I believe that's a felony. And he's plotting this kidnapping across state lines, which would make it a violation of federal law.