+ 1 for very Good Service from NVDC
Documented Vessels must be renewed every year. There's no cost for the renewal, you simply sign the form they send you and return it.
If you call the NVDC and give them the number and name of the vessel and the hailing port they should be able to retrieve the old documentation.
You will have to re-document, If I recall it's about $80.00....the paperwork is not that difficult...they will walk you though it and answer any questions.