If that is a copy/paste, it seems you didn't use the correct method name - in my sample code, the method is: Server.findForType(<object type>,<object id>)
based on your error, it looks like you ran Server.find(....)...
either that OR your vCloud plug-in is returning null... not sure... If you browse your vCO Inventory, are you able to drill down through the vCloud plug-in and see the orgs, etc... ?