Kevin McGeever, 68, turned up near Ballinamore in Co Leitrim on Tuesday night.
It is understood a couple who were driving in the area spotted him and picked him up.
Mr McGeever, who had been involved in a property development company dealing with luxury homes in Dubai, said he was abducted in Craughwell, Co Galway, on 27 May last year.
He told gardaí he had been kidnapped at gunpoint and held hostage for the past eight months and had no idea where he was.
The businessman's attackers had scrawled the word 'thief' into his forehead.
A spokesman for Irish police confirmed they are investigating an alleged abduction in Co Galway last June and gardaí in Ballinamore are also probing the discovery of a man on a road earlier this week.
Gardaí said there was no question that he had been held for months but said there was no evidence to back up suggestions a Russian gang may have been involved.
When taken to Ballinamore garda station, Mr McGeever had tea and biscuits and then a curry chip. He said a ransom had been requested but did not know if it had paid.
Mr McGeever, who has lost several stone in weight, is now recovering at Mullingar hospital.
A resident in the businessman's home village said: "It's just the most bizarre thing ever. The mystery thickens."