If you sniffed the packets, you'd see that the packets that get sent by the server after a success are of a different length than those of a failure (assuming same item and same level).
Try blocking the packets of that length, I dunno if that will work. Perhaps it would just eat your item.
Try blocking the packets of that length, I dunno if that will work. Perhaps it would just eat your item.

damn well that didnt work like i planned /shrugs i thought maybe u can pull whatever code that successes it and force it
(money) I'll let you know in seconds