Owen, 16, has now been missing for two weeks.
He left his house in Saltdean on Thursday, March 26, to watch the sunset in the Telscombe Tye area and has not been seen or in contact with anyone since.
In a message shared on FIND OWEN HARDING - MISSING TEEN Facebook page, his mum, Stella, said: “Dear friends. In this immensely difficult and uncertain time for me, what is constantly holding me up is the outpouring of love and support from everybody around me.
“Whether it’s working hard on the Facebook pages, going on searches, putting posters up, donating to the JustGiving page, kind words sent in a message, gifts for me at home of food or firewood.
“Just knowing everybody is thinking of us and praying for Owen’s safe return is incredibly beautiful, and I really feel all of you, and am so grateful.
“Thank you to everyone.”
A friend of Owen’s family has set up a JustGiving page, to support the campaign to publicise Owen’s disappearance, help organise searches, and provide financial assistance to the family.
The page has already received £2,720 worth of donations – greatly exceeding its target of £500.
Anyone who would like to make a donation can visit www.justgiving.com/crowdfunding/findowenharding.
Sussex Police this week renewed its appeal to find Owen. It confirmed one of two people who may have seen Owen on the evening he disappeared had come forward to assist police with their enquiries.
The force is now hoping to identify and speak to the other person pictured in CCTV footage released last week.
A police spokesman said: “New CCTV footage was released last week where a person believed to be Owen is seen walking along Hamsey Road, Saltdean, at 6.15pm on the day he went missing, Thursday, March 26.
“It is believed the person matching Owen’s description was heading south down this road, in the direction of the A259 South Coast Road.
“The man in the black hooded top has contacted police but officers are still hoping to identify and talk to the other person, who appears to be out for a run or other sports activity.””
Detective Inspector Mark Rosser said: “We have viewed this CCTV footage supplied to us by a member of the public and we believe this could be Owen.
“Within the footage there are two people who may have seen who we think is Owen walking along this road and one has now come forward. Are you the other person in the picture? If this is you, we would really appreciate it if you could make contact with us as you may hold vital information to our investigation.
“It’s been nearly a fortnight since Owen was last seen or heard from and we are continuing to extensively investigate the circumstances around his disappearance.
“We would like to thank the public for their support in our investigation and while we appreciate people would like to help with our searches, we are urging everyone to abide by Government guidance at all times.
“We are utilising all of our available resources to search locally and will, of course, link up with colleagues across the country if there is anything to suggest that he has travelled out of Sussex.”
Owen is white, 5ft 11in to 6ft, of athletic build, with short brown hair.
He is believed to have been wearing a blue round neck jumper, dark joggers and white trainers, police said.
If anyone has seen him or knows of his whereabouts, they are urgently asked to report it to Sussex Police online or call 101 quoting Operation Chartwell. If you see him, please dial 999 immediately.
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