I have experienced mufflers coming loose a few times over the years, and from my experience, the biggest concern is not "will the engine quit", but will that loose jangling muffler cause so much radio interference that I will not be able to land the plane. Personally
I would rather the part fell completely off, than lose my plane. IMHO you did get lucky, as you recovered your plane as well as your muffler. Nice going.

Lm