As a general rule, Saver tickets are non-refundable. In a wider sense, yes, you have to buy a new ticket.
You can find terms & conditions on the use of Saver tickets and the refund policy here: Refund on tickets in Switzerland | SBB help & contact
Get back to us should you have further queries.
PS: please see our English-speaking community for further travel advice and information: Questions and answers - SBB CFF FFS Community