You didn’t mention which type of sensor was being tripped. But from your description and the topic tag, I assume it is a V2 Motion Sensor.
It may not have been tripped by anything. It may be the sensor. There are countless posts and topics about false positive alarms from a hypersensitive or faulty sensor.
I have one sensor that I cannot use for monitoring. Way too many false positives. Something on the inside just isn’t right. I had to retire it.
It may be that you need to change the battery, factory reset it, and reinstall it.
I have another sensor that did the same thing. I did a factory reset, took the battery out, deleted the sensor, let it set for a couple weeks, put a new platinum battery in it, installed it, and have heard a peep out of it for well over a year.