Today a guy in my group hit his parked cart with a shot. I was going to come in here and ask if it is a penalty because it was a shared cart and the other occupant is a fellow competitor, not a partner or caddie. Turns out, I didn't need to because the answer lies in the first Decision of Rule 19. Decision 19/1 says that so long as the FC isn't actually moving the cart at the time, it and everything in it are considered yours. So, per Rule 19-2, the player incurs a penalty of one stroke and the ball must be played as it lies.
The thing is ... he lost that ball. After it hit the cart it either deflected OB, or some random direction that nobody saw and he had to replay. So the question is:
Does the lost ball "over-ride" the one stroke penalty and he re-hits lying 3 or does he incur both penalties since the ball clearly struck the cart before it got lost, and thus re-hits lying 4?? (He carded a 6 on the hole, so I know that he went with the latter option because he hit 3 more times from that point on)