Hello JoelD
Welcome to the SBB Community.
To cancel or change Supersaver tickets is impossible. Supersaver tickets are useful if you are 100% certain that you will make the trip.
In your case, you have to purchase a new ticket to Lucerne, or travel via Zurich to Lucerne. In the latter case you can use the Supersaver ticket to Zurich, as foreseen.
Kind regards,
Roland