Hypothetical ?? About Licensing

Several years ago, I was offered a warbird ride by one of the old timers at
the airport. So, of course, I took him up on it and had a great time riding
around in the front seat of an open cockpit biplane.

Now that the person has moved out of the area, I've been told by his friends
that A) He flunked his medical years ago and never got it back and B) His
aircraft, while probably safe, probably didn't have a valid annual.

OK, since the statute of limitations is presumably up and my flight with him
probably isn't verifiable anyway, I figure I'm free and clear of any
problems.

But, let's just say that either A) We got ramp checked on landing or B)
There was an accident with him flying the airplane (but w/o a license) and
yours truly riding along.

What would my exposure have been to enforcement action from the FAA, given
that I had every reason to believe that everything was on the up and up???

KB