I think the set of doors near where the number 10 is are in fact complete doors, separating the shipping area from the main entrance.
There is one thing that has been bothering me. Shelley and Lovelady are supposed to have re-entered the building on the west side, but all the doors on the western side of the building actually go to the basement. For them to get to the 1st floor they would have to climb the stairs in the north west corner or those seen in the floorplan west of the main entrance.
So, maybe there is something after all to the possibility saw both men, coming up those stairs, as she re-entered the building through the main entrance. There is, however, no evidence for it.