Muskellunge are found in Lakes and large rivers from northern Michigan, northern Wisconsin and northern Minnesota, through the Great Lakes region, north into Canada, throughout most of the St Lawrence drainage and northward throughout the upper Mississippi valley, although the species also extends as far south as Chattannooga in the Tennessee River valley. Several North Georgia reservoirs have stocked populations of muskie. They are also found in the Red River drainage of the Hudson Bay basin. So unless they were stocked specifically in the lake where this little bullhead came from, I doubt that a muskie is what bit it in half, more likely a snapping turtle.
However i suppose anything is possible.