An inquest has heard a 19-year-old who disappeared after allegedly being a surrogate mother was killed and put through a farm shredding machine.

The coroner investigating the disappearance of Amber Haigh today became angry with a witness, telling him "it is not a joke".

A couple Ms Haigh lived with on a farm at Kingsvale near Young in the central west of New South Wales, Robert and Anne Geeves, reported her missing in 2002.

That was five months after she gave birth to Robert Geeves's baby.

The Geeves told police they last saw Ms Haigh, who had a disability and the mental age of a 10-year-old, when they dropped her at Campbelltown Railway Station in Sydney to visit her sick father.

Today witness David Williams, who said he was also known by the nickname Sheepdog, admitted he once heard rumours Ms Haigh's body was "hidden in grapevines", but he said at the time he was drunk and stoned.

Mr Williams, who used to work in an abattoir, said the conversation started as a "practical joke".

He denied talking on another occasion about the "gang bang" and "torture" of Ms Haigh or about her throat being cut.

Mr Williams said he thought one of his colleagues had phoned police about Ms Haigh's disappearance because of the $10,000 reward on offer.

Another witness, Adam Blundell, said conversations he had with friends about Ms Haigh's body being put through a farm shredding machine were "a joke".

He said he was employed by Robert Geeves but had never asked his boss what happened to Ms Haigh.

Becoming increasingly annoyed with Mr Blundell's answers to questions, coroner Scott Mitchell said to him: "It's not a joke.... it's not funny."

The coroner told a third witness he was "acting like a clown and a buffoon" and "could get into serious trouble".

The inquest also heard Mr Geeves is now seeing another woman as well as his wife.

When Mr Mitchell asked the new woman, Ursula Kirk, if it was the case that she did not know or care about what happened to Ms Haigh, she replied "yes".

He then asked her if she was concerned about Mr Geeves's "poor track record", saying he has been acquitted of murdering a woman and associated with another one who disappeared.

Ms Kirk replied: "I feel everybody has a past."

The inquest has previously heard only months before she disappeared Ms Haigh told her family the father of her child wanted to use her as a surrogate mother.

The inquest at Parramatta continues.