My dad fell for this scam (sadly he won't admit it to his friends to help prevent them from falling for it). He did explain to me what happened: the social hacking was successful enough that the scammer may not have known you real friend's name!
In my dad's case, someone called and said "this is your son. I'm in London and my passport was stolen." My dad asked, "This is <my name>? Are you OK?" Then he asked why "I" hadn't called my wife, using her name. Now the scammer could say "I tried to call <her name>" and had some explanation I now forget. Thus the scammer was able to build confidence.
The really interesting thing to me is that the caller didn't even have my accent. When he finally called me, my dad told me that, and said though he noticed that immediately he was so worried about me that it didn't cause him to suspect anything!
I'm a parent so I can understand how some of your rational reasoning can shut down when you think your kid is in trouble. I now see that as you start to lose your marbles this can become pretty bad.