I've been thinking on this quite a bit, since I learned that the police wanted CCTV from Elsworth and adjacent streets, a gateway to the forest.
Why do they want the CCTV from there when indications seem to be that Sam was on foot until around 8ish? She would have been much further along on the trails by then.
I am thinking that maybe there was an after-party, when The Deck closed, and when he left that after-party in the morning he drove his 4WD along the "back route" through the forest to avoid booze/drug buses. And encountered Sam.
A route something like this (I used the walking variation so I could pick up the forest trails that his 4WD should easily have been able to handle). Where he could have ended up on Boak Road on his way home (to his parents place).
View attachment 489753
Google maps