(f) in any case where any export goods have been loaded without payment of export duty or in contravention of any
provision of this Act or any other law for the time being in force relating to export of goods,--
(i) such goods have been unloaded, or
(ii) where the Assistant Commissiner of Customs is satisfied that it is not practicable to unload such goods, the person- in- charge of the conveyance has given an undertaking, secured by such guarantee or deposit of such amount as the proper officer may direct, for bringing back the goods to India.