I was flying with my instructor when 10min into the flight the muffler fell from the sky. I tried looing but to no avail. When i went to retrieve the plane ( the engine quit as soon as the muffler came out) only the 2nd part of the muffler came off.

1) how do i keep this from happening
2) Where can i purchase only the 2nd half without buying a whole muffler

Engine: Mangum Xl .40