A family is warning travellers to check their insurance after an error filling in a form left them with an invalid policy and a £100,000 medical bill when their daughter became ill on holiday.
Katya Katalinic, 18, from Midhurst, West Sussex, had a brain haemorrhage in South Africa in February.
She had stayed on in Africa after a Christmas family holiday to Kenya.
Their insurer, Axa, said the policy was invalid because the family had provided incorrect information.
Miss Katalinic said she remembered waking up in hospital with people she did not know.
"I lost the ability to speak and read and it was pretty much like being a newborn baby," she said. "I had no idea about anything."
Her mother Marsha Katalinic had made sure the family were fully insured for the Kenya trip in 2022.
When her parents returned to the UK in the new year, Miss Katalinic decided to stay on for a yachting stewarding course in South Africa.
Her father Roberto Katalinic took out another insurance policy for her, which they tried to use after he and Mrs Katalinic rushed to Cape Town when Miss Katalinic was taken ill.
Mr Katalinic said he gave the details of the policy to the hospital manager.
"He looked at the screen and said 'you're not going to like this email'," said Mr Katalinic.
"Axa had got back to him, saying they were not liable and the parents will have to cover the cost."
Axa ruled the policy invalid because Miss Katalinic's trip to South Africa had started from Kenya, not the UK.
Mr Katalinic said: "There may have been 'the journey must start in the UK', which I assumed, well, it started in the UK, it didn't start anywhere else.
"The journey started here, in Midhurst in the UK."
Miss Katalinic is now issuing a warning to others: "You see stories about other people and you think how awful it is to happen to them, but you never really realise things will happen to you, so just make sure everything's in order, that you are covered and everything will be OK."
In a statement, Axa said: "The declaration presented at the point of purchase asks that the purchaser confirms all details are true, including 'that anyone named on the policy is travelling from and returning to the United Kingdom' and that 'your trip has not yet started'.
"On this occasion, the responses provided were not aligned with Miss Katalinic's situation and this was only uncovered following her claim. The policy was cancelled after we realised it was invalid and the full premium was refunded to Miss Katalinic."
Which? deputy editor Sam Richardson said: "I think they are being given the information, but it can be very hidden and requires perhaps an unrealistic amount of looking on the part of the consumer.
"The fact that a quarter of claims aren't paid is really concerning and suggests that these products could be kind of better constructed so people know what they are getting."
