Following nearly two weeks of evidence, a number of theories have been examined as to why he was there, and how he disappeared.

The eighteen-year-old was last seen being ejected from the Cheeky Monkey's bar at 11pm on May 31, 2019.

His family think one hypothesis that he tried to climb cliffs at Cosy Corner beach, fell and was swept out to sea does not align with his sensible, risk-averse nature.

Other theories include that he was disorientated due to intoxication, tracking towards the famous Cape Byron Lighthouse, or trying to find a beach party in Cosy's Corner with an unidentified person.

No evidence was found of a party on that night, or that Theo's phone was being used by somebody else.

His communications with family before his phone switched off just after 1am on June 1, indicated he was happy, alive and well.

The last backpackers to socialise with him at a hostel barbecue and the town bar all say he did not appear drunk.

Google data shows he looked up the route back to his Wake Up! hostel but walked in the opposite direction. It's not clear why he loitered at some cricket nets along the way for seven minutes.

A hat he was wearing was found in bushland on the route in the Arakwal National Park, but nothing else.

Officer in charge of the investigation Detective Senior Constable Philip Parker told the NSW Coroners Court on Wednesday about "new information coming in overnight".

It came in the form of a purple OPPO phone dropped in August 2019 near Cosy Corner, of similar description to Theo's but which belonged to a woman who said she had been partying there.

Det Parker was grilled by Theo's family lawyer David Evenden if he asked the woman how big the party was, or how it was organised.

"I think I just answered that," Det Parker responded.

He was also questioned on Thursday whether Theo's unique IMEI number allocated to his mobile device was used by someone else and if that was investigated early on.

"Those inquiries were done earlier by Louise Hawkes," he said.

Sergeant Hawkes from the homicide intelligence unit travelled to the area on June 14 to assist with the search.

"Was that shortly after Theo disappeared?" Mr Evenden said.

"Well, it wasn't before, that's for sure," Det Parker responded.

"Because if you hadn't, you wouldn't have known from the time that (Ms) Hawkes did her search whether or not Theo's handset had been used up until November of this year," Mr Evenden said.

"That could be correct," Det Parker said.

He said nothing was gleaned from the phone investigation.

The officer also walked the route Theo was said to have taken at night and found it "scary and intimidating," agreeing it was hard to believe a cautious person would do such a thing.

While contact was established with Theo's family as to operation details, at one stage a decision "was made by the hierarchy of the NSW police," to withhold documentary evidence.

But Det Parker could not speak further on that.

Search coordinator Senior Constable Amanda Vidler led missions on foot, in the air, under the sea, and down the cliffs using abseilers.

And following two separate psychic reports that Theo was in a crevice at the bottom of the lighthouse, she also searched there, but nothing was found, she said.

The inquest continues.

Australian Associated Press