Kevin Michael McGeever, who once traded property in the Middle East, turned up after being on a garda missing list since last summer.
Mr McGeever (68) was found on a road near Ballinamore, Co Leitrim, late on Tuesday night.
A couple found the tycoon in a disorientated state, covered in a plastic bag and without any shoes. A source today said he had also "sustained injuries to his body".
He is understood to have told gardai that he was dropped at the rural location by a number of men in a van and that he couldn't recall where he had been for the past eight months.
His partner Siobhan O'Callaghan is believed to have reported him missing to gardai in Cork. His last known address was in Clontarf in North Dublin.
But the fact that he was found on the side of a country road has left both family members and gardai baffled.
"It's all come as a real shock. We hadn't heard from him in such a long time. We just can't believe that he was found walking along a road in such a strange state,"one family member told the Herald.
Officers were today due to formally interview the pensioner in order to establish how he turned up at the side of a road.
He was found near Ballinamore, Co Leitrim, holding a torch and a mobile phone but had no money.
"He was covered in a plastic bag and wasn't wearing any shoes," according to Leitrim county councillor Martin Kenny, who spoke with the couple who found Mr McGeever.
"He told them he had been dropped off by a number of men in a van and he had been in the van for some time. So it certainly appears that he was being held against his will.
"Where he has been for the past months is anyone's guess, but it must be a great relief to his family."
Mr McGeever was today receiving treatment at Mulligar Hospital.
It is understood that he is being treated for malnutrition and dehydration. Gardai are hoping to speak to him today.
During the boom, he ran a successful property business selling luxury homes in Dubai to wealthy Irish and British clients.
When he was reported missing to Gort Garda Station last June, an address he had been using at Brooklawn, Clontarf, Dublin, was also included in the missing person report.
Although gardai were alerted by Mr McGeever's disappearance eight months ago, no formal appeal was released.