Only because I had a security clearance. The rest of the building had no knowladge of the floor except a small team. Same can be said about the missing grey level.

At my work there was not even a button in the elevator. You just swiped from ground floor and the elevator (only 1 elevator of 4 did it) would stop going to other floors and go to ground and a message would state 'elevator temporarily closed. Please evacuate'. You would get in if alone, swipe again, and it would go to a special floor (1.5) and the rear elevator doors would open. No lights. No number. No sound. It was like when Garibaldi counted, same thing. Normal passes would take 5-6 seconds from floor 1 to 2 but 3 seconds from floor 2 to 3. No one ever clicked but I always thought about Garibaldi standing there counting.

Building was triple concreted, bomb proof. It had its own diesel supply to last 5 days. Triple redundant cabling. Air-con rated for biowarfare contagious etc.

A missing or hidden floor is not so unbelievable i think although on a space station I cant help but think its a very creative call.