What code (line numbers would be best) in the unholy mess that is sessions.php gets executed when a user visits the forums after having his cookie time out from inactivity?
But seriously, I think this is what you are looking for. It is on line 308 in sessions.php.
PHP Code:
// see if user has been here recently
if ($ourtimenow - $bbuserinfo['lastactivity'] > $cookietimeout) {
vbsetcookie("bblastvisit",$bbuserinfo['lastactivity']);
$bbuserinfo['lastvisit']=$bbuserinfo['lastactivity'];
}