I was wondering how BG could not have been seen but by a couple of people and apparently not seen getting into a vehicle.
I wonder if he walked there from his house.
If so, he lived right along Bridge Creek which feeds into Deer Creek at the Monon Trail Bridge.
If he followed Bridge Creek from his house, he could pass under Route 25 and be basically undetected until he came up at the south end of the Monon Trail Bridge at the end of the bridge where the girls were.
He could have planned to march them down the hill to go to Bridge Creek but they ran and his plan was spoiled.
Here is a map I hammered out.
It's some work walking along a creek like that.. but there are always deer trails to make it easier.
View attachment 377425