No, that's how I know it wasn't a snake. A snake will eat eggs, sometimes a small chick, but almost never an adult chicken, even a bantam. They constrict their prey, but they never pull any feathers.
A lot of things come to mind, but usually they would all rip the chicken open, not just pull...
Not a snake. Not a broken neck from flying into the nest box. With the missing feathers it was a predator, but no way to know what kind with just that info.
Did you check for tracks?