Partial Outage in Apartment
Most circuit breakers have 3 positions: On, Off, &amp; Tripped. To a casual observer, the Tripped position may look like it is still &quot;On&quot;. Note that you cannot move directly from Tripped to &quot;On&quot;, you must go to &quot;Off&quot; first

https://www.anthonyphc.com/wp-content/uploads/tripped-circuit-breaker.jpg
Should you be concerned: Yes. It could have been a nuisance trip due to a momentary surge, but it could also be a real overcurrent condition. Inspect all the devices on this circuit. Look for frayed cords. If any of the devices are acting weird, replace them. If it happens again, call an electrician.
Did an incandescent bulb on this circuit recently burn out? Rarely, a broken filament will momentarily create a high current path.