This is what is in the book I have. It actually starts at position starting on turn 5, so I'm guessing the first 4 moves. It's a little different, so I modified it a little to get the result.
But yeah, 6... Nxe5 would have sucked. My only guess is he saw the open queen and couldn't resist.
By the way, since I know my game could have gone horribly wrong, and saw it during the game, I probably won't gamble like that again in a rated game.
It's a Legal Mate (or a variant), but it's an unsound sacrifice, as you noted. In your game, you would play 6. h3 and if Black plays 6......Bh5, then you would play 7. Nxe5.
You 'll have to see the Line, Jumps & Cooperation to prevent the CheckMate.
... Where I almost instantly *lost due to a Blooper because I didn't saw the Jump to the SmutterMate at first.... glad I wasn't Tired at that moment 
[Event "and on a Random Day I met..."]
[Site "Chess.com"]
[Date "2012.05.11"]
[White "odiouspariah2"]
[Black "Defence4Gizchehs"]
[Result " ?0-1? "]
[WhiteElo "1094"]
[BlackElo "1418"]
[TimeControl "1 in 3 days"]
[Termination "Defence4Gizchehs ?won? on time"]
[Variant "Chess 960"]
[SetUp "1"]
[FEN "rkrnbbnq/pppppppp/8/8/8/8/PPPPPPPP/RKRNBBNQ w KQkq - 0 1"]
1.d4 d5 2.Nc3 Nf6 3.g3 e6 4.e4 dxe4 5.Nxe4 Nxe4 6.Qxe4 Bc6 7.Qd3 g6 8.Bc3 Bg7 9.Nf3 Bd5 10.Ne5 Bxe5
11.dxe5 Nc6 0-1
* I don't see this game as a Win for Black.
I don't know what a Computer's Evaluation of this Position is; but Certainly not enough down to the min to lose.
I guess Personal and/or/nor Situational problems/Issues took the lead for him 
Now I cannot claim this Win as a Victory.
I do not like this.
I saw a mate like this in a book and thought "Lets see if they will be tempted by the queen." In reality, taking my knight with their knight would have really hurt. It was a huge gamble, but black went for it.