I am with John on an employee causing this. When any engine gets fixed it gets tested for a period of time then to shipping. I know the tech guys at MTH and that would not be something they would do. When they finish a repair they have to initial it. Jason would not let something like this leave his shop.
The fact a section of the sideframe was broken off and a gear floating about, I would be looking at Fed Ex rather than MTH. Sideframes do not get broken by a tech.