Peter Dixon discovered that the device, bought and installed in honour of his late father Ron, had gone missing from Millhouses Park on Father’s Day.
Now he has launched an appeal for information and a fundraising campaign for another machine to pay tribute to his dad who died 20 years ago.
He said: “We don’t want to say it was stolen because it might have been used by someone who really needed it and not returned.
“We don’t have any proof of that but obviously, it’s upsetting as it was installed to remember my dad.
“It was really upsetting to go down there on Father’s Day and find it had gone.”
Mr Dixon, aged 37 and a dad-of-two himself, said the box used to house the defibrillator was still there – and that there was only minor damage to the case, which he says appears to have been prised open.
He added: “I’m registered as the keeper of the defibrillator, so if it gets used, I get notified by the ambulance service by text.
“On this occasion, I didn’t get a message. I just discovered it when I went down there to make a routine check.”
Mr Dixon says the defibrillator had only been used once since it was installed outside Millhouses Cafe in the park last summer – but is vital for the local community in times of need.
He raised the £1,500 needed for the kit by running the Sheffield Half Marathon.
He added: “It was all in honour of my father so obviously we’d like to know what happened to it.”
Mr Dixon’s father died in 1998 from a heart attack while the pair were playing hockey together. Peter was 15 at the time.
Peter’s wife Millie said: “Ron was a big believer in community spirit and this was in his memory.”
“Hopefully someone out there will know something.”
If anyone has any information, they can contact The Star at [email protected] and messages will be passed on.
In the meantime, Mr Dixon is planning to run the Manchester Half Marathon to raise cash for a replacement. Visit www.justgiving.com/crowdfunding/peter-dixon-3 to donate.