DLC Key and Gearbox Support

Bought a key for Claptraps Robot Revolution way back when it was released through either Gearbox or the 2K store, can’t rightly recall. Got a sudden urge to play Borderlands again, so got my retail discs and my General Knoxx key from Direct2drive no bother. Trying to get my key from Gearbox is like getting blood from a stone. Has anybody else had this trouble? There is a link on the 2K support site for those with lost keys to enter their emails, but it’s broken and the support staff are asking for proof of purchase!