Rules - Golf ball mixup!

So what's the rule -- and the penalty -- for playing the wrong ball? It falls under Rule 15-3b, according to Bryan Jones, co-vice chairman of the PGA Rules Committee. Here's the official definition:
"If a competitor makes a stroke or strokes at a wrong ball, he incurs a penalty of two strokes.
The competitor must correct his mistake by playing the correct ball or by proceeding under the Rules. If he fails to correct his mistake before making a stroke on the next teeing ground or, in the case of the last hole of the round, fails to declare his intention to correct his mistake before leaving the putting green, he is disqualified.

Strokes made by a competitor with a wrong ball do not count in his score. If the wrong ball belongs to another competitor, its owner must place a ball on the spot from which the wrong ball was first played."
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 And remember this - 
Rule 12-2 -- which allows a player to lift his ball for identification 

Wrong Ball Played from HazardQ.A player plays a ball from a hazard (water hazard or bunker) onto the putting green. Once on the putting green the player realizes the ball he played was a wrong ball. What is the ruling?
A.In match play the penalty for playing a wrong ball is loss of hole (Rule 15-3a). 

In stroke play, the player incurs a penalty of two strokes (Rule 15-3b). The stroke played with the wrong ball does not count in his score for the hole. The player must correct the error by playing out the hole with the correct ball (his original ball). If the player is unable to find his original ball he must proceed under the lost ball Rule (Rule 27-1).