I used to be able to remember part numbers too... for locomotives when I worked on the railroad... but what's happened is my mind has been crammed to capacity with endless online account usernames and passwords and so these days I am lucky if I can remember what I ate for breakfast.
Memory is the second thing to go...
I work for the railroad now, and at least you only have to deal with two manufacturers, and only a handful of models now. It’s only a matter of what parts they have in stock at the warehouse, and how bad you need that power to build a train.