In what situation would the HTTP referrer header report Google when clicking away from a Facebook link? Not only is there no Google search field on Facebook, but Facebook also reroutes links through an intermediary page in order to hide the actual referring page.
I had assumed that Referer URLs were sent even if it wasn't from a link that was clicked. That's not true. (And yes, "Referer" is misspelt in the standard...)
> The Referer field MUST NOT be sent if the Request-URI was obtained from a source that does not have its own URI, such as input from the user keyboard.
If you go from that Facebook page straight to Google, it'll get indexed.