If the payment page reported a failure but your bank shows a charge, the amount is usually released automatically by your bank within a few days - a failed authorisation reserves the money without taking it.
Your seats stay held for 15 minutes after a declined attempt, so you can try again with another card without losing them.
If the charge settles and you still have no ticket, contact us with the date, the amount and the email used for the booking: we will locate the payment and either complete the booking or have it refunded.