He didn't loose his receipt. He never got one. I didn't get one when I ordered my Jeep hubs from Jim.
Warn expresses a lifetime warranty with all their hubs, so you should be entitled to a warranty. Did your Aunt send the payment via PayPal? If so, you may be able to get a receipt that way.
Jim, you should come on here and clear things up. If you know what he needs to do in order to redeem the warranty, tell him. I'd be interested myself. If he can't redeem the warranty, then you have a problem with your supply system, as that warranty asset is being lost somehow on the way from Warn to your customer.
EDIT: And I would not recommend a knuckle swap for 34s. Jeep hubs should be plenty strong enough for 35s of any kind on a locked axle. I run 35" ProComp Mudterrains, and have run 36.5" RVTs in the past, and that was with standard hubs. If you lock an axle and run big meats some care on the gas is required, even if you're running a D60.