Haha - yeah not quite the easy fix I thought it was. You'd need to weld a new hook on to secure it long term.
It looks like it was designed to have 2 hooks attach it. Have you looked for the hook on the other side of the car?
A more permanent temporary fix would be to move the grommet onto the other side of the muffler & attach that. You might also find that the grommet is still attached to the car on that side.
