Fixing online.php

After implementing filburt's "make your forum search-engine spiderable" vB modification, I've discovered that the Who's Online feature would simply claim that a user is viewing the "Main Index" when they were actually viewing a thread or forum (I have verified this using different computers).

So, using the original code from this post regarding a similar hack, in online.php, I changed:

PHP Code:

$loc=preg_replace("/\?s=[a-z0-9]{32}(&)?/","?",$loc); 

...to this...

PHP Code:

$loc=preg_replace("/(f)([0-9]+)(.html)/","forumdisplay.php?forumid=\2",$loc);
  $loc=preg_replace("/(t)([0-9]+)(.html)/","showthread.php?threadid=\2",$loc);
  $loc=preg_replace("/&s=[a-z0-9]+/","",$loc); 

This works, to a point. Who's Online now displays a user as "Viewing Forum" or "Viewing Thread", but it does not specify which thread or particular forum they are viewing. Does anyone know how I can fix this?