Notification when beacon is not reporting

I use simple bluetooth beacons and the beacon app for switching the presence of users. But unfortunatly the batteries of the beacons go empty. So I had an issue for the last 12 days. The devices where not found by my Homey and flows aren’t triggered.

I can not find a correct flow to notify me when this device is not reporting. Anyone any suggestion?

can’t you create a flow with the trigger card “a device has not reported”?

No, I think thats not working. Simply because you can’t point the beacons in the ‘and’ section.

sorry I don’t have beacons,
maybe use a variable that is set when a beacon is detected and check with a timer if a beacon is detected in a period of time and reset the variable.