Not seeing the file, in the location posted above, on Mac OS X 10.6.8.. Have not tried to get it through code, as it may be in a slightly different location..
If there is one thing I've learned the hard way, is that if Apple supply an API for accessing elements, and the code has been posted to do so, use it.
I know that the MBS costs money, the MacOSLib is free, although for some things it can be harder to wrap your head around.
The reason being, in 10.8.4, Apple can move the image file update the image file or a bunch of other things. if you use the API, your app will still get the correct image. If you directly link to it, and it moves, you'll no longer get it or if Sandboxing then prevents your app from accessing that location, you won't get it.
Another advantage for using the correct mechanism is that you'll also get the Retina version if your app is being used on a Retina display.