Spanish Motorway Safety

Wouldn't have minded reading this about five years ago.   I was driving home on the M50 round Madrid - on my own one quite Sunday afternoon when I was over-taken by a car containing four guys who signalled for me to pull in onto a narrow hard-shoulder.   Being naturally suspicious I stopped some distance behind them and stayed on the road with the hazards on.   One bloke got out and came back to me showing some sort of card at my window.   I hadn't lowered the window but opened my passport and pressed it against the glass, at the same time making a show of opening my phone to use.   During the stalemate he raised a thumb then walked back to his car.   I drove on shaking slightly with fright....