Smoke detector did not alarm but the fire dept was dispatched and our house alarm was tripped

Last evening our house alarm was triggered and the Fire Department dispatched to our home without us hearing the smoke alarm. The alarm is right outside of our bedroom door and there is no way we would not have heard it had it actually been tripped by smoke. When we called this morning to discuss what had happened, the representative had us go through the requisite steps to ensure proper functioning of the smoke detector. When we started, the red light was not flashing, nor was it flashing in the kitchen smoke detector. Effectively we've been living with non functioning smoke detectors for an unspecified amount of time which is quite terrifying and antithetical to why we have the system in the first place! We have an older system and apparently the base station may have been responsible for not communicating with the smoke detectors properly and tripping the alarm. Why don't the smoke detectors automatically convert to battery if the system is down? Or do they? This seems like it could quite literally be a fatal flaw in the system.