On September 3rd, Ulrike Demmer, deputy spokesman for the German government, said that the head of the German government was to meet in Warsaw with President Andrzej Duda. There were also plans for a conversation between the Chancellor and Prime Minister.
The President of Poland learned about the meeting with Chancellor Merkel from a press statement by the German government. Only later did the representatives of the embassy contacted the President's Chancellery to arrange a meeting.
Polish newspaper, Rzeczpospolita (Republic) reports that on Saturday President Duda will be in Silesia region to celebrate the 41st anniversary of the Katowice Agreement that ended Solidarity strikes there.
It is entirely possible that Chancellor Merkel was trying to show President Duda where is his place.