Sorry, I understand what you are saying now.
Neither SmartThings nor Google is trying to assign fault. As you are aware since you were using it, previously the Google Assistant integration with SmartThings would discover the sound bar device with a device handler of “Samsung OCF Network Audio Player”. The integration offered limited functionality for controlling the sound bar, but as you’ve noted, being able to switch the device on/off via Google Home fulfilled your needs.
I understand feeling that something was taken from you. The nature of the integration is that as you add and remove devices in SmartThings which are supported by the Google integration, those devices are automatically added and removed from the Google integration. Supported devices are added and removed automatically in an effort to effortlessly link SmartThings to Google. When support for these devices was removed several months ago, the device was automatically removed by the integration which resulted in your device disappearing from Google Home.
This automatic action definitely had the opposite effect of making your life easier as you have spent great amounts of time trying to figure out what happened. For that I apologize. Had this change been better communicated I imagine you would still be disappointed but less frustrated. Hopefully your negative experience can be used to encourage more communication in the future.
The unfortunate news is that there isn’t a workaround or trick to getting the device to display as before. The good news, as Lars noted, is that the removal is only meant to be temporary and the goal is to offer even more control of these devices through the Google integration. When support for the device is returned, the device should automatically be discovered by Google Assistant which will give you control via Google Home that you desire.