Rule 18: Ball at Rest Moved

I was playing golf with my family last week and one of the craziest things happened. I hit my second shot onto the green and it landed about three feet from the hole. I marked my ball with a coin when I got up to the green, but I did not pick up my ball. While I was surveying my putt a gust of wind blew my ball into the hole. What is the ruling? Should I have replaced my ball?