Well it finally happened. I discovered that Rachio is monitoring for leaks when no zones are active. 
I did not even know that is a feature! 
This happened twice today, at 4AM (when I have my flex schedule running before sunrise) and 7AM (when it was time for the fixed new grass schedule).
As I have a master valve, clearly the issue here is that it was having an issue shutting off and one of the zone valves was stuck open as well. Since than I’ve done maintenance on all of the valves (took them apart, cleaned them, put them together). Couldn’t find the leak or any large debris, but hope that took care of it.
The reason for this post, besides 
kudos to Rachio team for having this in place, is that the unscheduled leaks do not seem to show up within webhook notification system and none of the data I can find via the app or email seem to indicate the duration of the leak. In my case the master valve seem to have shut off the leak in the notification after a short time (none of my zones are flooded), but it would really be great to know how much water was dispersed.
Feature suggestion: Add a notification and data about duration and water consumption of unscheduled leaks. This would be very helpful to adjust moisture level of the zone(s) which were being potentially flooded. And, in case the master valve is part of the system, if system could pulse the MV in case the leak is pressing for longer than X minutes, it could potentially stop the leak before the owner wakes up and/or help arrives.
Thank you, keep up the good job.
Gene 