My buddy and I were playing our weekly match when I hit a drive just off of one of the cart paths. I had my eyes peeled for the ball as I drove us down to go look for it, but neither of us saw it anywhere. Suddenly, I saw the ball come shooting out from under our cart. Figuring I had run over it, I stopped the cart, got out and grabbed my ball. I put the ball back where I was pretty sure I had run over it, but I wasn't sure what to do next. I figured that, since it was an accident, I didn't deserve any penalty, but my buddy said he thought I should have taken a couple stokes for moving my ball. Was he right?
— Eric Rooney, Ontario, Canada
Even if you don't have to follow the rules of the road in your golf cart, you still need to follow the Rules of Golf. You may not have moved the ball on purpose (or even really moved it yourself), but you are still responsible for causing the ball to move, which is a violation of Rule 18-2. You were right to replace the ball as close as possible to its original position, but you should also have given yourself a one-stroke penalty for causing it to move.
Believe it or not, the fact that you were the one driving is the mitigating factor here. If your opponent had been behind the wheel when the cart hit your ball, it would have fallen under Rule 18-3a, and you would have been able to replace your ball without penalty. So next time you hit one near the cart path, offer to sit shotgun for your buddy just to be safe.