I see that many cars have two rear fog lamps and it only seems to be particularly old or low cost cars that have one but my Passat only has one, but I wonder if it is meant to have two?

I only think this as the plastic bulb locating sheet on passenger side in the rear cluster through which you poke all the bulbs has all the electrical connections (live) for another matching bulb (there is only a fog lamp on drivers side). There is a scored line on the plastic which looks like it should/could be popped out in some way and a bulb inserted. Did someone forget this at the factory?!