Mistake on my part. I was doing a transfer where the item was originally sent to the wrong user by the gm. I was supposed to send the item from the wrong user to the correct user but I didn't realise that the wrong user had already sent it to NinjaScourge already.
Because of that and the way the system for transfers works, when I went to transfer the item to NinjaScourge from the wrong user it took the item from you instead since NinjaScourge had already got the item and sold it on to you.
The transfer registered the item Id of the dread tail and sent it without actually looking where it was sending from, resulting in the error.
I can't give a great description as I'm on mobile atm but I've sent it back to you and corrected the error. If you want more information about why it happened feel free to shoot me a PM.
Tl;dr you did nothing wrong. It was a bug in the item transfer system on our end.