To help some more, when you know Ford is
NOT going to take you down their repair road further than they have to. I've found that using or making fasteners work using the local hardware stores to be more beneficial in specific cases - like using those speed nuts with a Stainless Steel (SS) bolt - with it's head threading up from below, on the fixed fastener side, the speed nut will hold the bolt in place when it's tightened and then you can use the simpler wing nut, or hex nut to sandwich the removed plastic piece to the fixed housing - the speed nut holds the bolt in place once it's tightened. By using the speed nut like a jamb nut, the bolt can hold itself and you can install the part back onto the bolt and thread on a convenient hex nut to hold it in place.
I do this on several areas of the car, the front bumper skirt - the wheel-well fasteners as well as several points for the headlight for their own plastic rivet with setscrew are oftentimes stripped or drop out from the vibrations, wind whack and air pressures from highway driving (plastic distortion) from the wind pressing against the car will bend and even stretch plastic and in some instances of passing cars their wind whack from their wakes can break those fasteners much like how a simple low-MPH impact can shear off the rivets leaving the plastic dangling and even more subject to damage and stress.
Now, granted it would look like hell and may make some people re-think their worth - but if you're past warranty, Ford is not obligated to help you in supplying something it feels it's not worth holding a bin or two at dealerships for people that can fix fasteners on their own time - it's easier to shop-out the parts needed from sources and turn their heads the other way when it comes to such repairs - they are not going to cite warranty in cases of broken fasteners - they'll make you pay for the work anyways. Why have them do this to you? When a simpler repair in a location that isn't noticeable unless they get fussy - they'll see the other damage causing this type of repair and refuse to patch the work as a quick fix unless the entire job is completed as a crash repair you didn't want to pay for nor have as damages recorded on inspection in a visit.
Many an oil change place has "miraculously" repaired horrible noises from under vehicles caused by dealerships or lazy mechanics for not putting back in screws from their last oil change. Some vehicles use splash or road debris guards using these same plastic rivets. They also use tabs to hold them, but if they aren't screwed together - that splash shield can tear off.
Owners takes car in for oil change - tech removed guard, changed filter - drained oil - replaced filter and plug - refilled - and drove it out to the lot to wait for the owner to return for it - not noticing the hardware left behind when he forgot to screw the guard back in place once the bottom side was completed - so the plastic eventually sagged far enough to get caught in a whack of wind or got tugged and dislodged by road debris causing the skid protection it had, to scrape on the ground - abrading itself and transferring that into a noise filling the cabin and scaring the Hades out of its occupants - all because of a lackadaisical attitude a mechanic had over properly re-installing a splash guard which took on it's own life and made a horrible noise until someone was able to see it and fasten it down correctly.