Regarding the winner... A player with class will say "nice shot" and concede the point. They will acknowledge that they had lost the point anyway and won't use the loose ball as an excuse for a do-over.
I played a mixed match a few months ago where a ball rolled onto the court as I blew my return of serve. When my partner (appropriately) called a let I replied that the ball didn't have anything to do with my return (it didn't) and we gave our opponents the point. Five minutes later another ball rolled onto the court as I served an ace. Our opponets called a let and we replayed the point without complaint. Of course, I knew it was a chicken call since they wouldn't have returned the serve anyway - especially after I had just conceded a point in a similar situation.