Teresa Scott met with Detective Inspector Mark Benefield, the officer in charge of the investigation, several times over the 12 days she was in Auckland, but had to leave the country today.
"We are frustrated that there haven't been any corroborated sightings of Carmen and her belongings since June 27, but we have reassured Teresa we will continue in the hunt for her daughter," Mr Benefield said.
"We have been frank with Teresa and have acknowledged her worst fears - that the circumstances of Carmen's disappearance are sinister.
"We're disappointed we haven't been able to give her some closure or genuine hope but there are several phases of this investigation to go and we will stay in touch with her as much as possible."
Mr Benefield said the Operation Keppel team still has a lot of work to do following up on CCTV footage that may be of assistance as well as continuing to sift through information about Ms Thomas given to the team by her associates and friends.
He said it was important that anyone who recalled seeing her dark Nissan Pulsar car anywhere between June 27 and July 13 - when it was recovered by police in Hamilton - should contact the investigation team.
"Anyone who has seen Carmen since June 27 - or any of her previously publicised personal belongings like the distinctive turquoise handbag - needs to contact us on so we can put as much information as possible into the mix of the investigation into her mysterious disappearance," he said.
