Yeah, the cashier isn't going to know squat about your card. I've been on that end of it and customers get frustrated with you when you can literally do nothing about it besides maybe try to put the card number in manually or have you try to swipe it once more (which usually doesn't do **** but it shows the customer you tried).
But, anyway, I think anyone in your position would feel pressure from all those eyes on them. You shouldn't beat yourself up about it. All you can really do is give them a new form of payment, call your bank and see what the deal is, or leave. But please don't get an attitude with the cashier :3 It sounds like they could have been more accommodating but there really isn't much they can do.
take one day at a time
anything else you can leave behind
only one thing at a time
anything more really hurts your mind