So… you would also say then if he had made a photocopy of a $20 and tried to buy a candy bar with it and a cop saw it he wouldn’t be taken to jail? I’m pretty sure he would be, or there is at least a ZHe can suspect the printout is fake. He could perhaps issue a ticket. He can't dish out a criminal punishment without getting a court involved, and the court would give you a chance to explain your side of the issue. There's no way you'd be convicted of anything for showing a valid TRUST certificate to a law enforcement officer.
The place to dispute a law enforcement officer is in the controlled environment of a courtroom, not in the field.
Of course the officer was wrong here and it was a legitimate document, but if there was some sort of official FAA document the OP forged it is certainly possible he could have been taken to jail.
I am curious to see if this actually happens to someone. This whole process of telling folks to save these docs and print them out themselves is kind of ridiculous. Though IMO it’s better than the alternative of over regulation.