I've now been on the Black side of this trap twice. After the first time I was sure it was just a fluke, but... it seems to arrive out of a natural-looking series of moves that just happen to not work together.

Black to play.

Yeah Bd3 is bad.  Although I would go ahead and play Kh1 if I know the knight is going to be lost.  After queen takes, you can try e5. threatening to win the queen.  But black is okay if he just trades the pawns.

I don't quite see what you mean, but I'm interested. The Chess.com analysis didn't pick up this idea in the analysis. Can you put it in a diagram?

Steeve it honestly seems like you misplayed something in the opening.  If this is the Scheveningan, the bishop should not be on g5.  Which Sicilian is this from?  If it is Najdorf something went off in the opening.  Can you show me the beginning of the game?

It was reached after a rather odd line in the Sicilian that turned into the Sozin Attack.

http://www.chess.com/opening/eco/B86_Sicilian_Defense_Sozin_Attack

In less-seen Sicilian lines that tend to transpose (Bowlder Attack, closed Sicilian), I like to just stick to my preferred setup, which is pawns on e6, d6, a6 early. The initial play went: