If you notice it wasn't bought by the National Football Museum or any institution - historic football shirts will have an international market - the seller will have realised this. I guess the time for Boro to have bought was over a decade ago when there wasn't perhaps so much auction interest.I would have thought there would have been a grant or something to cover it. Shame really.
It is a real shame that it has gone away from public view and you would thought also left the area. Could it have left the country? The buyer could remain a mystery of course.