The three workers, hired to level out the couple's garden in view of a house extension raised Tracfin's – a service from the French ministry of finances tasked with fighting money laundering –suspicions after one of them cashed in two checks worth 270,000 euros ($361,000) and 30,000 euros ($40,000) into his account.
Called in by the police services to justify these unusual transactions, the worker immediately caved in and revealed the whole story, according to one of the police officer cited in Paris Normandie.
Read More Hidden riches: 10 sought-after treasures
He revealed that after several days of working in the garden, the mechanical shovel dumped against a solid object and the workers found themselves looking at glass jars filled with 600 gold coins and 20 U.S. dollar coins from 1924 and 1927 as well as 16 gold bars, each weighing one kilogram.
Hidden from their clients' view, the three workers – aged 20, 33 and 40 – secured the bounty, removed it from the site and contacted a local coin collector to cash in on the treasure. Estimated at 900,000 euros ($1.2 million), the treasure is thought to have been buried during World War II.
According to the investigations, the three thieves "treated themselves" by buying cars and motorcycles but ultimately acted "like good fathers", choosing to invest money in life insurance or renovating their houses.
Since their confession, a Land Rover, a Citroen DS3, a Peugeot 3008, a Suzuki GSR and several hundred thousands of euros have been sequestered.
For the unfortunate couple - who were unaware of the theft until police officers contacted them - retrieving the treasure could still take some time. Under French law, if the bounty has an historical relevance, the State can hold the bounty for up to five years.
The couple involved in the case have been allowed by the court not to reveal to the press their names, their address or when the theft took place.
Furthermore, the law also states that if the treasure is not found by the owners of the property then the owners must give a share of the treasure to the people who uncovered it. Whether or not the three workers will get some compensation is now up to the Court.
Read MoreX Still Marks Sunken Spot, and Gold Awaits
Follow us on Twitter: @CNBCWorld