Fathers desperate appeal information son's disappearance Theo Hayez Belgian ...

The devastated father of a Belgian teenager who has been missing in Australia for 17 days promised his youngest son he would bring the 18-year-old home. 

Laurent Hayez travelled to Byron Bay to help search for his son Theo, who went missing in the seaside suburb on May 31.

He was last seen leaving the Cheeky Monkey bar at about 11pm and never returned to the WakeUp! Backpacker hostel, where his passport and belongings were found.

His father made a tearful plea to the Australian public to not give up on his son, and said if witnesses were 'scared to come forward' they should send tips in anonymously.

The devastated father of a Belgian teenager who has been missing in Australia for 17 days promised his youngest son he would bring the 18-year-old home

The devastated father of a Belgian teenager who has been missing in Australia for 17 days promised his youngest son he would bring the 18-year-old home

'I promised Theo's little brother, Lucas, that I would bring his brother home,' he said.

'Please, help me keep my promise to him.'

Laurent Hayez thanked everybody involved in the search so far and said he had not given up hope on bringing his son home.

Police confessed they remain 'baffled' by Theo's disappearance and are exploring every possible line of inquiry.  

They have been working alongside Belgian police to build a character profile on Theo and agree his disappearance is out of character. 

'We're baffled as to what's occurred, but let me just say - we're not ruling anything out. We want to conduct all lines of inquiry and we're keeping it open as we speak,' a police spokesman said.

Murder police from Sydney have flown to Byron Bay to help find Theo Hayez (pictured)

Murder police from Sydney have flown to Byron Bay to help find Theo Hayez (pictured)

The fresh appeal comes after his cousin and travelling companion Lisa Hayez revealed a WhatsApp message was sent from his phone in the early hours of June 1.

The phone has not been active since.

On Sunday Miss Hayez has posted an appeal on Facebook, asking if anyone knows who he last contacted.

She wrote: 'Unfortunately it takes ages to WhatsApp to give any information to the police so if you could share this post so someone who knows someone who works for WhatsApp could help us to get these informations ASAP!'  

Theo was travelling on an eight-month gap year with his cousin and was due to return home a week after he vanished.    

The 18-year-old was looking forward to returning home to start his university course studying maths and science following and eight month trip around Australia

The 18-year-old was looking forward to returning home to start his university course studying maths and science following and eight month trip around Australia 

His mother Vinciane Delforge told a French broadcaster in Belgium she is holding out hope her son is safe and well - but said his disappearance is entirely out of character.

'We would love to believe that he met a girl and had a fling... and that's why there's no sign of life,' Ms Delforge said. 

'But that just isn't him, that's not his style.' 

She said her son was a 'meticulous planner' who had thoroughly researched his gap year to Australia in the months prior to leaving his home town.

'He is a

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