Would you get into the left hand seat of an aircraft without verifying the circumstances of the flight?
No, personally, I wouldn't. But I don't recall a recent occasion when evidence confirming my verification of those circumstances has been left on the ground, either. So far, I've always returned to tell my side of the story.
If I were in the position of the "CFI", I would be a great deal happier if I had evidence that supported my account that a pilot who had once refused to make a particular flight as P1, had subsequently changed his mind and agreed to make the flight which was, at least with hindsight, patently illegal.