What is printed on the screen if you add the following code above those 2 lines you found earlier:
It should print out that text, a number, and then the rest of the page should be white.
Code:
echo 'Detached shoutbox height: ' . $vbulletin->options['dbtech_vbshout_height_detached'];
die();
It should print out that text, a number, and then the rest of the page should be white.