I guess I don't know what SriLanken cultural norms are about this sort of thing, but at least here in the US, it wouldn't really be insulting to go to the gift giver and say that you really like the card, but it looks like it's defective, so you want to do an exchange or an RMA, and need the receipt.
Still, based off the SN of the card, it should be pretty easy to tell if it's under warranty or not, so I probably wouldn't worry too much about the receipt for an RMA. Follow Thomas' advice, and you should probably be good.