I was wrong, my wife said it was fine dirt. At the same instant the driver side vent switch to full heat while the passenger side stayed cool. Then the driver side switch back to cold. The car has fifty thousand miles on it , 2005 and a convertible. I do practically all the work on the car and did not know about the cabin filter. Here are a few pictures of what we took out of the duct from the passenger side.

Zoom in for a better view to try and identify