It was his first day, and Arthur had wasted no time in making a mental layout of the building. Sure, he'd studied the blueprints and technically knew where everything was, but that didn't compare to actually being there physically. There was something about it that ingrained the map into muscle memory, letting him navigate almost without thinking.
The supply room was usually only of cursory interest to him, but again, it helped to know where things were.
He just wasn't expecting to find someone in there, much less Tony Stark.
"Shit, I'm sorry," he covered easily, pretending to be embarrassed. "I was looking for central filing. I'll just–" he motioned to the door.