Examiners do cite non-patent literature (NPL), and yes they can trust Google. I have seen rejections that literally have a screen-cap of Google search results.

But yes, NPL is rarer than patent prior art citations ("Determinants of Patent Quality" by Bhaven Sampat is one study that has some numbers). This is primarily because patents are already authored, classified and organized in a way that examiners can easily search, so they typically find the necessary "ammo" they need to make a rejection more quickly there.