Well, search may have bugs (or undocumented features) too, I have googled content from other pages on this site (related to Metallica).
Page 6 for example: https://www.google.com/search?q=%22Listen+up+you+fags+metall...
Which goes against the original mission of Google to "organize the world's information and make it universally accessible".
A "bug" could be an option, but I don't expect that to be the reason. It's too easy to find examples of forgotten content. And I don't think a bug of that magnitude in Googles core business would go unnoticed.
Which core business are you referring to?