Hi gafar
No you're pretty stuck, I'm afraid.
What happens if the Deeds are gone - for good? A Vendor would be well advised not to sign Contracts where Deeds are missing until (a) they have been found and (b) a closing date without delays can be fixed or until its quite clear the Deeds are absolutely gone, not coming back but can be "re-constituted" with appropriate indemnities and insurance.
Its probably not a great idea to be emigrating while at the same time trying to sell a property ( sorry, I know thats not much help!) because when problems arise, as here, its just so much more stressful trying to fix them.
Nowadays, its not too hard in any event to arrange closings where clients are abroad what with e-mail, fax, mobiles and couriers. So, it may be just a question of finding those deeds or losing your current purchaser.
mf