Musso, has anyone - Theo's family, the local searchers - recreated Theo's presumed movements from that night? At the same time of night, on the same day of the week, in the same directions, using their phone in as similar a way as possible? (obviously, not alone, due to possible dangers)
I know that this is something that the police do (as in the case of Karen Ristevski) when they are trying to determine an accurate timeline, and what exactly happened, in a crime and/or the aftermath of a crime.
It might be enlightening for someone(s) to do that. Especially the PI.