Typically, if the EMS senses a fault, it will disrupt power through the EMS until the fault is corrected. In the event of a low voltage/frequency condition, it would temporarily shut down power and once the condition was corrected, it would then reapply power to the trailer. There would be no indication of "previous interruptions" recorded in the error codes. They only show "current faults" not "historical faults".
So, there would be no way (on the EMS) to determine if power had been temporarily interrupted. In every RV that I've seen, the microwave clock will not reset, so if power were interrupted by the EMS, the microwave clock would be blinking "00:00" or "--:--". That would inform you that power had been interrupted, but you would have no indication of how long.
You could buy a digital "max/min" thermometer to place in the RV. That would give you a record of how cold or how hot the interior of the trailer was while you were gone. That would give you some indication of about how long the power was off. You can buy two "max/min" thermometers for $10 on Amazon:
https://www.amazon.com/Digital-Refri...in+thermometer.
I'm sure others have different ideas on how to monitor the power status, from expensive "call my cell phone" systems to other ideas on how to best know the power status.