Maybe that is why I start off by checking known VW Group part supplier's web cats to get hold of part numbers etc - then with that info you can check that aftermarket suppliers are or are not supplying the correct parts. This comes in very handy when walking into places like ECP and getting handed what they think is what you need - learned by experience, once bitten twice wiser! It might annoy them when you question them, but it can save a lot of wasted time/miles/gallons.
I also have a habit of checking and recording the VW Group part numbers of "wear and tear" parts when I buy a new car, that works for me very well further down the line with a car.