I need a soft copy of bill that i lost about my iphone4 i bought from Denver Apple Store@ 27th August 2010?

As i said on header:

I need a soft copy of bill that i lost about my iphone4 i bought from Denver Apple Store@ 27th August 2010?

How can i get this because my phone is simlocked from AT&T but i bought the device without a conract i paid 650 dollars cash.

I can't find the store e-mail adress.