I don't feel sorry for anyone involved.

First the guy had it coming anyway and should have seen it coming, that his disqualification would be hidden forever.

If the company had a live coding interview, his incompetence would have stood out immediately, if he couldnt come up with a FizzBuzz in his own free time

Also, the author acted negligent to his friend if he knowingly let him go into that mess without warning him about the consequences.

Maybe I'm interpreting the term friend wrong but the author should have warned him anyway that he is not ready, given what he'd known about the guy.