Think you know the rules? Try this question

Question: Your second shot on a par 5 comes to rest where you see it enter a large bush.  When you arrive at the bush you see a ball in the bush and know it’s not going to work so you declare the ball unplayable.  Dropping the ball for Lateral relief under Rule 19.2c for a ball in the general area will get you out of the bush and playable. Now lying 3 you play to the green. 

On the green after marking, lifting and cleaning the ball you discover the ball in your hand is not the ball you played from the tee.  How did that happen?  What do you do now?

Answer: The ball you located in the bush must not have been your original ball played from the teeing area.  When you took lateral unplayable ball relief you did so not knowing the actual location of your original ball. That is not an option for lateral relief under 19.2c .  Even though you dropped a different ball it still became your ball in play. 

Since you didn’t know the location of your original ball (ball was lost) and played the dropped ball to the putting green you were playing under stroke and distance but from a wrong place.  For a lost ball the only option was to return to the spot of the previous stroke made for the second stroke.  Given the distance involved in the mistake it likely would be considered a serious breach.

Your only option is to return to where you played the second stroke and complete the hole from there.  If you failed to do that you would be facing a disqualification.  If you do correct the error, you were lying 4 on the green then adding the General Penalty 2 strokes for play from a wrong place plus any subsequent strokes in completing play of the hole from where the original second stroke was made.  It is never a good practice to assume a ball is your ball in play.  Always identify a ball before making a stroke.