Walk of shame.

There's a trade off:

Since I moved to the city, I've not been outside naked. I've locked myself out several times.

When I lived in the country, I went outside naked all the time, and never locked the doors. The keys were always in the ignitions of the cars if I never did. Originally Posted by Enchanterlingum

There's a clue for you designers; a call box on every floor for emergencies like this. In the middle or near the elevator. Think original Star Trek.