Jo, a 15-month Staffordshire Bull Terrier ran away as he was being walked near Bercy Village in the 12th arrondissement of the east of the city.
Caroline, his owner, immediately feared the dog had been stolen, as often happens with that breed of dog.
Within minutes of the dog disappearing she launched appeals on social media sites and specialist “pet alert” websites.
She and her husband then trawled Bercy Village desperately hoping to track down their pet.
But Jo was long gone. In fact he was in Châtelet in central Paris, Le Parisien newspaper reports.
Luckily he hadn’t been taken by any dog thief, but instead by Line 14 of the Paris Metro.
Jo had apparently got on the Metro at the stop Cour Saint-Emilion after apparently after having simply walked through the barriers and descending the steps of the platform. Although there is a suggestion he may have actually taken the lift.
The fact the dog was able to get through the barriers without a ticket will not surprise frequent users of the Paris transport system.
For some reason Jo then got off the Metro at Châtelet, one of the main transport hubs in the centre.
And like many of us have done in the past, he then seemed to get lost in the underground network of tunnels
The dog emerged on the platforms of RER train network which links central Paris to the outlying suburbs.
Luckily for Jo, before he could board a train that would have taken him far from home, a passer-by took pity on the mutt and took him back up to the surface.
She then handed him over to police.
But Jo wasn’t wearing a collar so officers were not able to contact his owners.
Normally he would have been taken to a pound for stray dogs but a police officer also felt sorry for Jo and took him home in the hope of finding the owners.
A colleague then spotted the online appeals and the following day, less than 24 hours after Jo had ran away, he was returned into the grateful arms of Caroline.
“It's a miracle,” the dog's owner said.
“The policeman’s two children were disappointed when I had to take him away. If he has any puppies they will be for them,” she told Le Parisien.