He probably gave her the recognition signal. I have a hard time believing that there wasn't any communication with someone beforehand.
I don’t know about this girl, but I do know of another instance where a guy had been watching a school bus and taking notes on who got out, when, and where they went. This individual managed to catch a 13 year old off guard, and lured her, whereby he kidnapped her and took her somewhere and held her captive for several days, about a week. He kept her in a shed, as I recall.
After about a week, she was either released or managed to get away. She gave police a great description of where she was held. Somebody who knew the guy recognized her description of the place, and turned him in.
The victims do not always know their assailants. But the assailants do study up on their victims, either in what they can say to lure them, or something else that catches them off guard. Most of the time, only a few seconds are all that’s needed.