I had exactly the same problem with an early 2010 diesel model. On changing gear there was a short grinding sound, the gear popped out and then the engine cut off. The car never started again. A mechanic confirmed there were fairly big chunks of metal in the sump. Does yours have a fairly high mileage?
I've got an unused Forester load carrier for sale if anyone is interested. The box from Subaru lists the part as: E3610SC500. The manual lists the part numbers as: E3617SC500 / E3610SC500 / E3610SC550.
Price would be £40 plus whatever it costs to ship it.
Cheers.