Ellis was an alias name for an unnamed source, and is protected by shield laws in Ohio. Even still, the reporter has an obligation to reasonably thoroughly investigate such a claim, leaving ultimate liability on the news organization (and they have deeper pockets than "Ellis" I am sure).
The damages incurred is the most interesting aspect to me...not really sure he could claim damages yet. A harm to reputation could happen down the road that causes damages, but I could see "token" or punitive damages for the time being. Could he prove that being named somehow lost him friendships to get actual damages? Relationships? A summer job opportunity? He may be able to conjure up some claim to damages.
No doubt in my mind that SI at least showed simple negligence (as said before, Klein will be a private person, so that is all he really should need), and quite possibly a reckless disregard for the truth. Correct me if I am wrong, it is late and I ain't a lawyer yet