Apple Itunes $50. ITunes gift card cancelled Cupertino, California

I received 2 $50 ITunes gift cards from my mom approximately 3 years ago.  I redeemed one right away with no problem.  When I just tried to redeem the the second one, by entering the code on the gift card on ITunes web site, I got the following message "The gift certificate or prepaid card code you entered has been cancelled".  The Gift card does not have an expiration date on it.

I contacted Itunes customer support and was told that Best Buy cancelled the card and that I must deal with them.  I did not tell them where the card was purchased so they had this information on file.  I told Apple ITunes that I have a valid, paid for, unreturned ITunes gift card and that they should honor it, to no avail.  Why should Best Buy be able to cancel my ITunes gift card?

I contacted Best Buys customer support by phone and was told that nothing can be done without a receipt.  Why do I need a receipt to use a gift card?  Who keeps a receipt for a gift card for 3 years?  Neither Apple or Best Buy will say why the card was cancelled.