Was the maple neck 'bare' wood? If even a slight sheen, shoe-polish will only sit on the surface and eventually rub off. To darken the maple, you would need to sand any clear-coating off first before darkening (however you choose to do that).
Appeared to be completely flat to me and from what I had read in research on these necks they are oiled and nothing else. Next step if it does rub off would be a more intrusive refinish on it, but we'll see how it goes.