Just checked the code and it should give you the UA in the mail, here's the code that does it
PHP Code:
$message = "DATE: " .$DateOfRequest ."\n\nUserAgent: " .$_SERVER['HTTP_USER_AGENT'] . " \n\nhas visited \n\n" . $vbulletin->options['homeurl']
. $_SERVER['REQUEST_URI'] . "\n\nFound In Your List As " . $bots2[$iz] . "\n\nRegards, \n\nBan Spider Mod";
see the bit that says
PHP Code:
\n\nUserAgent: " .$_SERVER['HTTP_USER_AGENT'] . "
that should show the useragent!?