Nightmare! sorry to here this I really feel for you, good luck getting it sorted.
I had a slight issue with my rear defuser/splitter come away from bumper at one side, eventually got the dealer who I bought the car from to agree to fix it through my local Honda dealer they said rear bumper had to come off and refit it putting all clips back how they should be, it would cost £120 which they charged the original dealer.
Today I have fitted my RallyArmor mudflaps and when I took the rear protection panel off underneath the car on that side I see two *uck off big self tappers screwed through the splitter top into bottom of the bumper!
I feel like they should have explained this to me and I would not have minded now I feel like I cant trust them.
Anyway mudflaps should be considered by all owners of this car because......
These flaps should defo come with black hardware.