Car Stall problems of the 2012 Honda FIT

I brought my Honda Fit 2012 to my mechanic with issues of a misfire in cylinders 1 and 2. He thought it was a simple replacement of the spark plugs (only 51,000 miles on the car) and maybe a coil pack replacement. Once he removed the spark plugs from cylinders 1 and 2, he saw the tip of one of the spark plugs ground had broken off into the cylinder head and the coil packs and spark plugs were worn and covered in a blackish soot. He informed me that this meant that the spark plugs has wiggled loose over time and extreme pressure had caused this issue. And since no one has ever touched my engine, beyond a Honda dealership for an oil change, that this was a manufactures defect when installing the plugs in the first place. All the movement caused the threads to wear away on cylinder 2, so I took to my local dealership thinking it would be covered by Honda, but they less than helpful. They stated my mechanic had no idea what he was doing, and did the damage. They said there are no current recalls or campaigns, but it took me 10 secs on the internet to find TSB's issued by Honda, nothing the exact same issue I am having! this has put me in a fight with Honda of America to cover this very costly repair.