1) Are you sure it is stored correctly in the eCart to begin with? What happens when you display that column in the cart?
2) We can add debug code to the pp_confirm.php page to see if it is passed and try to figure out why it isn't viewable. After line 24 add debug code:
var_dump($_SESSION);
die();
Then view source and post the result to me in the private area. I'll take a look and see what I think.