The process for measuring a calibration course goes to great lengths, insisting on a steel tape and compensating for temperature changes to determine the overall length accurately to a fraction of an inch. I'm don't believe that re-establishing an end-point when the nail cannot be found is a good practice, whether by triangulation or other means. It doesn't take that long to layout a cal course. Just my opinion.
I also think that all cal courses should be certified. If I go to the trouble of measuring a cal course, it doesn't take much more effort to draw a map and submit an application. It makes the cal course available for other measurers and would be useful when validating a course.