Kevin Crennan's sister has described the manner of his reappearance as a fantastic twist of fate.
Last week the Irishman was arrested in Colombia after he was found near an area controlled by a left-wing rebel group. It was the first information his family had heard about him in seven years.
"It could be a major twist of fate or a coincidence - who knows? - but it shows he was meant to be found, no matter what," said Ms Ann Rogers, his sister, who lives near Sydney in Australia.
"It is fantastic the way the whole thing happened. We are all over the moon," she told The Irish Times.
Colombian immigration police have said Mr Crennan (37) has been sent back to his point of entry, Venezuela, for failing to meet his visa requirements. Ms Rogers said he would now "probably be heading for a few days of quiet retreat".
Ms Rogers posted details of his disappearance on the Internet, at www.missing.ws, a site dedicated to finding missing Irish people.
Mr Crennan, who holds an electrical engineering degree from the University of Limerick, moved to Spain from London in 1993, when he found a job teaching English
A year later, he was planning to attend the soccer World Cup championship in the US, but moved house a few months beforehand. After that, "he lost contact suddenly with his family in Ireland and his brother in England", said the site.
Ms Rogers said the family were initially not worried about the loss of contact, but grew concerned after a couple of Christmases.
His mother, Ms Mary Crennan, said she believed he was in the US and perhaps did not make contact because he was working illegally.
She said: "I did not want to be letting it worry me; you can't be worrying all the time." Mr Crennan has two brothers and a sister.
Ms Crennan, speaking from the family home in Abbeyleix, Co Laois, said her son did not have strong political beliefs, but he perhaps "leant towards socialism a bit".
Mr Crennan told reporters last week he had gone to Colombia in May en route to Peru and was staying in guerrilla territory, controlled by the Revolutionary Armed Forces of Columbia (FARC) out of curiosity.
Speaking while in custody, Mr Crennan said he wanted to "chat with them and see what their point of view is".
Ms Crennan does not know why he disappeared without contacting his family.
The latest news she heard about her son was that he had been teaching English in Bogota to, among others, officials from the attorney general's office there.
He had also been living, for two months, in an agricultural commune near Bogota.
Ms Rogers said her brother was "free spirited and independent". She had spent time in South America and had discussed it with her brother. It was "always in his mind" to go there, to "cut loose and go and be free".
She said she had already emailed her brother, but had not received a reply yet. She hoped he will "get in contact in the near future".
Ms Rogers said the family had not known if he was alive or dead. Her mother was especially relieved at the news. "She is an elderly woman. Maybe she was afraid she would die without seeing her son again."
Ms Crennan said she was "quite happy now" and hoped her son would telephone soon and she may see him again "sometime in the future".