A Misunderstanding?

Just as Zhang Heng was looking around the second floor for the woman in the black tennis uniform, the latter reappeared behind the counters. As she reached out to pick up a black magnet from the floor and placed it back into her pocket, she allowed it to be sucked into another white magnet.

She then squatted down and tried her best to make no sound as she walked along the counter. First, she saw the bathroom sign. When she walked in, however, she realized that there was only one exhaust fan connected to the outside. The woman in the black tennis uniform moved a trash can and stepped on it. She looked outside and found that it was an open parking lot.