Some videos on YouTube are not available to mobile devices. This restriction applies via the website (when accessed through a mobile device) as well as the YouTube app. This happens when someone has filed a "copyright claim" against a video (that is, they believe the video infringes their copyright, or "Content ID" matched the video against some copyrighted content, most likely the latter given that you're searching for a commercial music recording), and the alleged copyright-holder has told YouTube to allow their content to be used on desktops but not on mobile.
Even if it's possible to work around this, it would probably be illegal for us to make this information available to US citizens, because that's circumventing a technological restriction under the meaning of the DMCA. This applies regardless of whether the copyright claim is well-founded.
You can get the actual song by buying a recording of it, or by downloading it through some music-pirating service.