It is not a bug, it is working as designed. For example, if I have a smoke alarm, should it restart openHAB and reset my alarm Item’s state to undefined if I haven’t had a fire in my house for a long period of time (I am becoming a better cook)?
However, there is a simple and easy way to deal with this in Rules. See:
and see the following for a slightly simpler way to do it if you only have one or two Items to keep track of:
Both work on the same principle. Set a Timer and every time the sensor reports reschedule the timer. When the sensor fails to report for a certain period of time the Timer triggers and it will send you an alert and do whatever else you want it to do.
