yeah that's exactly right, that's what i was referring to, where black ends up losing the rook. What is it called?
Bishop and knight trap in the opening

It's barely even a "trap", it's just a double attack on the pawn, which is very easily defendable by Black. It does seem to be very common amongst beginners though, so I'd guess that there might actually be a name for it.
Recently I won in about six moves using this trap and I've played lots of games where I had some success with it. When you move the bishop and knight so they are both attacking f7/f2, and if nothing is done about it the opponent usually ends up losing a rook, or worse. (or having to move their king to the second rank - I know many people think it's good to develop the king early but not like this! :D)
I cant remember what it's called though, and also when the opponent guesses what Im trying to do, I'm often quite stuck as to what to do next, and carry on the attack. So I'd be interested in what people had to say