I found Mike Fitzgerald by searching baseball-reference.com for a player that was a Pinch Hitter, had one Plate Appearance, had 4 RBIs, and where the Home Team won (and I sorted by date). After searching that, I looked at the box scores until I found one where the GS happened in extra innings. I could be wrong, but I didn't find any other one's that fit the criteria after Mike Fitzgerald in '88 (at least not for a walk-off).
I think you should question the guy that's in charge of this trivia question, because Hundley was on the Away team. So, if the criteria was in fact for a walk-off, then he's giving the wrong answer.