[danilocesar]

because he gets emails from the unit when it happens.

I had a script in a raspberry pooling my UPS each minute asking if the unit was running on AC or battery, and dropping that info into a file when it changed. I know the software/daemon can also do something like that.

[jaywalk]

Yes, but in this case he wouldn't have gotten an email since the UPS failed right when the power went out.

I actually had the exact same thing happen to me a few months ago. A power flicker so brief that it didn't even reset any of my clocks, but it caused one of my cheapo standby UPSes to give out.