When Sarah's cat went missing and she received a message from somebody claiming to have seen her, she was hopeful.

But the Sydney student, 18, who had posted on Facebook and put up posters about her missing pet, was shocked to discover the person was trying to scam her.

They had created photos of a cat similar to hers using AI and were demanding money.

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"If this happened to me it's going to happen to someone else," she told 9News.

Black cat Cinda, who is 16, escaped at Middle Street in Kingsford in Sydney at 9pm on May 5.

The person who contacted Sarah, by email, claimed to have "found her".

They posted photos that looked like the cat in a car and on a sofa.

But when Sarah questioned them further, they said they wanted $200, with some to be paid by Apple gift card.

"They were like 'I spent my last buck on her'. They were like, 'Are you going to compensate me?'" she said.

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And while like any cat owner Sarah said she'd hand over any amount of money to get her cat back, she started to get suspicious.

She said the photos didn't seem to be her cat.

"I just knew it wasn't her," she said.

She showed them to her boyfriend who also realised something wasn't right.

The messages were also written with strange grammar.

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When Sarah questioned them, they threatened they would "go and sell her".

Sarah said she was onto them but went ahead with their demands to meet at a local supermarket.

She went with her mother but nobody turned up.

"I'd give everything I have for her but we knew it was a scam, " she said.

While the police told her there's nothing they can do, she also reported what happened to Scamwatch.

She's warning other pet owners to beware.

"What they're doing is extortion and it's a crime," she said.

"I would say question it – don't just rely on your own judgement."

Cinda has green eyes, and one of her eyes has brown discolouration. Underneath the black fur on her neck is sparse white fur.

9News has contacted Scamwatch.

If you can have seen the cat, contact reporter Sarah Swain on ss****@******om.au