Hello Rules Guy: I thought my approach shot on a par 4 might have landed out of bounds behind the green, so I hit a provisional ball (into a bunker). My brother and I checked behind the green but couldn't find my original ball. Then, as I approached my second ball, I came upon the first one. I chipped that on and two-putted for a bogey. Unbeknownst to me, my brother had found my first ball (the one I finished the hole with) out of bounds and had tossed it in my direction without telling me. Was I right to have played it?
— Peter Scarcello, Utica, N.Y.
Sometimes it pays to be a little oblivious. According to Decision 15/10, there is no penalty for playing a wrong ball (in this case, your first ball that was out of bounds) since you were unaware that it had been thrown back inbounds. Once it was made clear that you had played the incorrect ball, you should have corrected the error by returning and finishing the hole with your provisional ball, with no penalty aside from the ball out of bounds. Had you already teed off on the next hole, you would get off scot-free with your bogey.