He could have seen her come out of the house to get on the bus. Some kids wait just inside the door until the bus comes and then run out, rather than wait on the side of the road. So he'd know she did in fact live in that particular house.
I don't know, I believe the bus story. My guess is the idea of kidnapping a girl had been rattling around in his head for some time, years maybe. I think all the details, the gun, the tape, disabling the trunk thingie, shaving his hair, etc. had been planned in his mind for some time. And something about Jayme that particular day clicked for him and he decided to act on it.