As his owners desperately searched for him in the streets and back alleys of Lee-on-the-Solent, the adventurous ginger tom who headed for the sun was discovered in Bilbao.
Four-year-old Sandi's owners, Tim and Patricia Austin, of High Street in Lee-on-the-Solent, had feared the worse when, completely out of character, he failed to come home last Friday.
The immediately began putting up posters and handing out leaflets to people in their neighbourhood, but to no avail.
So they couldn't believe it when three days later they got a phone call to say Sandi he had been found alive and well - in Spain.
He had been discovered onboard the P&O ferry the Pride of Bilbao, on it's Saturday night sailing from Portsmouth to the Spanish port.
But Tim, 67, thinks Sandi was cat-napped. He said: 'We got the phone call out of the blue - we couldn't believe it.
'We know our car wouldn't have gotten into a car or van with strangers voluntarily - even we can't get him into a car. We think he got out of the vehicle on the ferry when someone opened the door and he ran.
'Him being microchipped has been absolutely key to his return - without that he would probably have been put down after they found him.
'And P&O have been fantastic. He's been well looked after.'
Although Mr Austin and his wife Patricia now know Sandi is safe and he has been brought back to Britain, he can't come home for up to six months because of quarantine rules.
Matt Ford, from Animal Health, the government agency for the safety of animals, said: 'The first we knew about it was when P&O contacted us from their Portsmouth office on Monday to say "We've got this cat, what do we do with it?".
'We were able to tell them what to do and once they could get it tested for a microchip they were able to get us the data.
'We were the first people to call the Austins - it had been quite a traumatic time for them. They were clearly very happy and rather emotional to find that their pet was safe.'
Brian Rees, P&O spokesman, said: 'Since he was found he's been treated like a VIP - he's had a cabin to himself for the reurn journey and been dining on chicken and salmon. 'I think most of the crew have had a cuddle - they'll be sad to see him go.'
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