He doesn't quite make it that far. As he makes his way back into the main lobby of the building, two things happen simultaneously, as he steps out the employee door into that room. First, his invisibility vanishes, likely stripped away by some sort of spell. And second, he'll notice the rather large group, of heavily armed guards, with several obvious spellcasters, at the back. Multiple crossbows are aimed at him, as well as heavily armored and shield-bearing soldiers, at the front.