It takes her a moment to notice the lack of Kate because Steph naturally assumed she would follow. About twenty feet away from the column Kate ducked behind, Steph stops and turns around in a slow circle.

She doesn't understand the point of this exercise, but she can guess it's a joke, "I was trained by the World's Greatest Detective, you know. I can find you."

Yeah, she just called that out on the train platform. What of it?