the guy is 4 million dollars richer! 
He's not. They took his money back, since he didn't get them legitimately.
how did they get his money back?
.... he never really "had" it ... like all those people with bitcoins in Mt. Gox, they only have an entry in a spreadsheet ... Mt. Gox holds the priv. keys itself.
"You can;t sell what you don't own", is made real by bitcoin, but so few chose to really use it.