How does that explain Polarik’s decision that mine was a fake?
Yours was indeed fake, in terms of its provenance, the claims you made simply could not be true.
And by the way, Polarik was correct in his appraisal that it was not a genuine 2001 vintage document, as your finding the actual receipt did indeed demonstrate.
You know that you didn’t deal with Polarik fairly. You know what you sent him. You know what you didn’t send him that he specifically asked for. Stop trashing him and go on about your business.