I followed your directions and there was nothing in that room. I went to the room opposite of it and saw this key. Do you mean this one? Because it doesn't work for the door (also, it has the same name as one of the three keys on the top floor).
The other door next to the generator room contains nothing, and there is no key card that will open it. All the other usable doors have a 4 digit code, but this one has 5, so I wouldn't have to worry about accidentally set one of the access cards to the same code required to open this door.