Barty had not chosen to go down each entire row in all its long length when to the first row was enough for him to get a better feel. And he wasn't sure if the intruder/s had wandered off that much. And he was in a rather good location, near the main entrance. Depending on how efficient a search was, it was a place to walk through more than once. And really, if the person were able to be a regular visitor, why sneak in - unless they meant to steal something. But hmm, not the time to think about that.
Returning, yet again, to head around to the next aisle at the main entrance, Barty's eyes peered into the darkness again, to make sure no one was still there. Swiftly, but as silent as before, Barty moved around to the next row. His eyes peered out to make sure - something felt, it felt like. Hmm, Barty waited and watched.