I think the article does a very good job of showing the utter ignorance of politicians, and, to an extent, the journalists reporting the story.
How would anyone know where the banknotes are?They’re purposefully not traceable, and the minute they are, their use will decline even further. The anonymity they provide is a valuable personal freedom, and one of the few ways to balance government interference in everyday life (and personal spending).
That the BoE know the approximate value of the notes (calculated by knowing how many are issued and destroyed of every denomination) is an indication of what information they do have. And it is as much information as any other Central Bank in the world had over their notes and coins.