I appreciate the guidance. I wasn't aware of the ability to create a trigger for such events. I am testing it now on my test server. My concern is it won't actually fire if disabled by the system. This event is not even logged in the audit log, so I'll wait and see. I did test by creating a job that triggered on trigger deactivation. The job had one task, send SMTP email with the variables you listed above. Unfortunately the variables are of no use. While the variable stated PrevTask, the task details included in the email were for eth SMTP notification task. Also the Last Trigger fired description was the trigger monitoring for trigger deactivation!
However, simply getting the email notification is a start. I can probably determine what trigger was deactivated fairly easily as I only have a few culprits which commonly deactivate. I'm testing now to see if it truly fires upon system trigger deactivation.