Carlos Sánchez Ortiz de Salazar, now 47, disappeared from his home in Seville province in 1996 during a bout of severe depression.
After nothing was seen or heard of the man originally from Bilbao for 14 years he was legally declared dead by the Spanish authorities.
But two weeks ago a man claiming to be Carlos was found by two mushroom pickers, who stumbled across his camp in on a thickly wooded hillside outside Scalino, a town in Tuscany.
The two foragers had been eager to find some mushrooms in the woods after a weekend of heavy rainfall, but after having no luck, the pair decided to venture off the footpath to try and turn their fortunes around.
But instead of finding mushrooms, they found a trail of plastic bottles and dirty plastic water canisters which they followed until they stumbled across the camp of the man, who reportedly had "a dirty face and large beard".
Terrified, the two men ran back towards the footpath but returned a few hours later with the head forest ranger. After reaching the camp, the man came out to greet them.
“I'm Spanish, my name is Carlos and I've been living here since 1997,” he said. “I don't want to live among people: now that you have found me I need to get out of here.”
But before Carlos packed up his camp the group asked him to prove his story, at which the hermit pulled out a battered, faded and long-expired passport bearing the name Carlos Sánchez Ortiz de Salazar. Before leaving, the group managed to snap a photo of his passport with their smartphones.
Using the photos the foragers were able to notify the authorities about the man's presence in the woods as well as the missing persons' association, Penelope, in Italy and its counterpart, S.O.S Desaparecidos, in Spain.
The authorities quickly tracked down his family, who arrived in Italy on Friday.
“That's him – that's our Carlos,” sobbed his parents when they saw the photo of his passport. “He is alive and that is the most important thing,” they told journalists from Corriere Della Sera.
On Saturday morning his parents joined a search party that went into the forest where the mushroom pickers had found Salazar, but he had done as promised and moved his camp.
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“There was no sign of him,” said the disappointed mayor of Scarlino, Marcello Stella. “Who knows if we will find him again.”
But his parents were resolute and vowed to continue searching the forest until they could find their son, who they had believed dead for so long.
“We respect his will and his freedom but we're not leaving until we have held him in our arms again – even if it is just for one last time," his mother Amelia said.
It is not known how he managed to survive in the wood for so long – some theories suggest he found a way to cultivate food, while others suggest he has survived thanks to midnight raids on dustbins at the edge of nearby towns such as Scarlino.