A couple days ago I was playing a friendly casual round with my new SIL and also getting to know his dad a little better too. My 3W second shot on a par 5 hit smashed directly into his dad's ball as it came down (he was laying 2 about 6 feet in the right rough). My ball kicked back about 10 yards and also further out into the right rough. Horribly thick but at least not OB. His ball was propelled forward a few yards and ended up about 10 feet out in the fairway. I figured I had to play my ball where it ended up and did so, but since we were 100% playing for fun I had no qualms when he asked to play his 3rd from it's new lie in the fairway. Really there was no way to replace his ball exactly anyway since we were 200 yards from the collision, but in an official situation would that be the proper ruling?