I know your frustration, but how can a company that ceased operations do warranty workHowever, they should have honored the warranty. That's what irritated me most.
BTW did you check to see if there was spark. From what you explained in post, it could have been the magneto got loose, and snapped off. The clearance between the moving parts of a magneto are about .015 inch. that is equivalent of the thickness of 5 hairs.
I got a new lawn mower from a family member. They had it for about 2 months, and it went bad. They purchased another one, and gave me this one to do whatever I could. I investigated, and found the head gasket to be blown out.
$8 later and been using it ever since.