The Mysterious Locked Bathroom

I work at a mental hospital, and recently, to prevent patients from harming themselves, the hospital decided to replace all the doorknobs. The only issue with these new doorknobs is that they frequently malfunction, locking people inside the rooms, particularly the bathroom doorknobs.

One day, while the hospital staff was in a meeting, we heard screams and cries for help coming from the end of the hallway. We rushed to the scene and found that someone was locked inside the bathroom, desperately banging on the door and screaming. The voice sounded like that of a woman. We kept trying to reassure her through the door while preparing to unlock the door with a key from outside. However, the key inexplicably wouldn't work, leaving us baffled. It was as if the key didn't fit the lock at all. We suspected that the maintenance department may have mistakenly changed the lock when they replaced the doorknob.

The woman inside the bathroom grew increasingly hysterical, and we could hear her violently pounding on the door and screaming. Panicked, we sent someone to the maintenance department to find a master key, while others attempted to force the door open from the outside. We kept shouting at the woman to stay away from the door, but her terror had reached a point where she couldn't even hear our voices. Suddenly, the bathroom fell into complete silence. Not a sound could be heard from inside, which made us even more frightened.

We frantically tried to force the door open, but it remained locked. Some even considered finding an axe. After what felt like an eternity, someone from the maintenance department arrived with a master key. Strangely, as soon as they approached, the door swung open on its own without even using the key. We rushed inside, but to our bewilderment, the bathroom was empty. Everything was exactly as it should be, as if nothing had happened. We meticulously searched every corner, finding no signs of anything unusual. We quickly counted the people and realized that all the staff and patients were present, with not a single person missing.