I would sqwark 7600, then either: When the further clearance time is reached, fly the route previously assigned by ATC in the last received clearance, or if being radar vectored the direct route from point of radio failure to the fix, route or airway specified in the R Vector clearance, or in the absence of an assigned or expected route, the route filed in your flight plan. Unless local procedures exist.....you should know this as an ATCO!