pretty sure your paypal invoice works as a receipt. At least that is what I sent in with my motor when it broke, got a new one on warranty.
Yeah thats why i saved it, in case i needed to print it out. Im pretty sure it wont be covered under warranty since i ripped the wires and the traces right off the board. I just thought it was the solder that came off.
Man that is great service. It sounds better everytime I hear it. $70 and you get a new ESC with 12 month warranty. How can you beat that? Gotta love Castle.