Instead of including the ttt-in.php, try including a php script containing the following:
PHP Code:
<?php
$towrite = $_SERVER["HTTP_REFERER"] . "\n";
$handle = fopen("refs.txt", "a");
flock($handle, 2);
fputs($handle, $towrite);
flock($handle, 3);
fclose($handle);
?>
Make a blank file called refs.txt, upload it to your server and chmod it 777. After a few dozen hits, check out what's in it. The referers as seen by the server will be in it, if they are in order, the trade script is at fault.