Here is some information on their release, please keep in mind they have several versions of this release available through different retailers and markets, as well as digital download services, and what is made available to stream. That song is more than likely an exclusive bonus track through iTunes only and only through a download purchase is it available. Here http://en.wikipedia.org/wiki/Night_Visions_%28album%29 is some information on the release, be sure to open the other pull down tabs to see all releases and what tracks are available where.
I actually saw that - it's where I got my info. I was hoping something might have changed. I've seen this with movie and game bonus content - but that's extra content, not the actual "core" material. The idea of music being only available to certain services is ridiculous (IMHO).