Dear Sweta,
Once you export the consignment custom give you the foreign exchange control copy for your bank where you send the original documents for payment.
if your export payment is not recoverable, which already show in the books of your bank which should be write off within 6 months of the period from the date of export.
so you can give the request letter to your bank and describe reason why you are not able to recover the payment.
Also, You have to cylinder all export benefits taken by you against this shipment
Hope your equiry is solved.