Well, we do know that L's father called her at 3:11, got to the trail parking at 3:14, and after not getting a hold of her, entered the trails to look for them. Originally, I figured the killer to be gone before L's father's call at 3:11, but after the PCA, my impression is the killer was with them longer than that, so now I have been curious if L's phone ringing at 3:11 maybe prompted her to tell him that her dad was there looking for them. She could have hoped that would spook him off. IMO, if this did happen, he likely killed them soon after that call.
It makes sense to me because then the killer would have had reason to avoid the entire trail and park area, knowing a father was there looking for his daughter and her friend, and maybe going to the bridge, or off trail to do so. The killer could have exited out the cemetery, or any point from the woods east (as far as RL's) or west (as far as west of Hoosier Harvestore, but that would have taken him awfully close to the trails) and crossed to the north side of the street to avoid the parking lot across from Mears (where L's father was parked), and all the buildings between that lot and the CPS lot. We don't know if he was seen on the Harvestore cameras, but it certainly wasn't listed in the PCA.
I don't know if I'm making it very clear, but I feel like the killer wanted greatly to avoid the entire trail area, including the woods that run along the trails, because he knew L's father (or other people in general) could spot him. But in order to get back to his car, he had to do something. Would he just walk the road? IDK...I think the field behind Harvestore makes the most sense, but even that would have brought attention to him...some guy walking through the field. My best guess, though.