If a drone detects it lost wireless connection, it should be able to use reverse path (from memory) and be in coverage area.
eg: A cellular network operated drone, if it finds a coverage gap in the designated path, it should continue on its path expecting coverage will be restored after some distance. If that does not happen, drone shall use the trail /path from memory and return to the point where it had connectivity.
eg: If a wifi operated drone, crosses its zone, it should get back until it gets connected again.