I have been briefly following Theo's case and unless there was foul play, I believe he must have fallen somewhere around the headland. Every year people are injured or killed trying to walk around the area there. Here is an example:
'Devastated': Mum's heartbreak after son falls down cliff if Theo tried this in the dark while intoxicated, he could easily have followed what appeared to be a walking track, only to find himself stuck on the side of a steep, dangerous cliff after following a goat track. It would be a disaster, nobody would know he was there, he would have to try to get back down and could have fallen a long way onto rocks below. His phone could have been knocked out of a pocket and laid in a rock crevice, pinged the nearby tower, went flat, or the tide came in and washed it, along with Theo out to sea. As for the hat, it was not known if the hat belonged to Theo and there has been no information about testing results, but I hope the exact location of where it was found was recorded, as if it was Theo's (which I doubt),
then they need to search above and below that area and also check winds the night he disappeared, to calculate what direction it may have been blown into the bush from.