The page numbers (and title) displayed at the top of the Lynx screen are added to the document by Lynx. Since they are not part of the document itself, the WHEREIS command (by default the "/" key) will not find it. Lynx does allow you to search for text that is actually in the document, so if you need to jump to a certain location, you might try guessing what text is at that location.
Would you like to view the key bindings for the version of Lynx you are currently using? This won't work if you are not using Lynx, by the way.