i agree with you that it's probably not random. in order for a random scenario to work, a kidnapper hunter would have had to just happen to walk by in the woods as she was walking out of her house and think to himself "hey i should abduct that girl" and then immediately run out of the woods and grab her. it's not like she was hanging out by her car.
it makes way more sense to me that this person was someone she at least knew a little bit. id guess the person was waiting for her, walked out of the woods and probably called her name. she was probably confused as to what the person was doing there, but didn't panic until he grabbed her or maybe even said something. she screams, he hits her, maybe threatens her or her family, and then whatever he does/says is enough to convince her to follow him to the woods. as others have stated, he likely was unaware that her brother was home and probably thought he'd have hours before anyone noticed her missing. the fact that he still didn't get caught says he was either a) really lucky or b) a guy who really planned this ahead of time.