transfer of apple care

I just bought an iphone 3gs 16gb from a friend. He has bought the apple care from AT&T for the iphone before selling the iphone to me. The apple care is up to October, 2011.

I have asked apple how to transfer the apple care under my name. Apple said that it will need the receipt for apple care from my friend. However, he cannot find the original apple receipt either.

What will be the solution in this case?

Please let me know. Thanks.