this method worked for me 1 week ago.
1.Go on Shpock and search for XboxGiftcard and find one with includes the
back of the Gift Card, (most of them.)
2.Look in the bottom left of the Xbox gift card and you will find the Serial
Number, copy that down in a Notepad.
3.Go to Xbox live support and tell them that you have accidently ripped the claim
code part and can't redeem it and say that you heard the Serial Number can help get it.
4.They should ask for the Serial Number just give it to them and SE your way
through and you should get an Xbox Giftcard.