Your ticket was not cancelled. The train was cancelled.
What you need to understand is that you do not have a ticket for IC 185, you have a ticket for travel from Stuttgart to Zürich. While discounted tickets are indeed limited to the train you selected during booking, the moment that your train gets cancelled your ticket becomes a fully flexible one. So you can travel on alternative trains, without needing to do anything. Just find your train, get on, and show your ticket when the conductor comes.