some people (myself included) have cracks in the door handle covers, but your is the first I have heard about falling off completely!
I think that is the concern for this trim piece. If the button and fob aren't working and you have to do the little push & tug procedure to get the handle out so you can use the key tucked into the fob, you could pop the trim off. Also anyone messing with the car, whether maliciously or not when the handles are extended could do the same. Hopefully this is one of those odd build problems that affects just a few and can be remedied with a new trim piece.Coincidentally, just today, I smacked the rear edge of the left rear door handle with the back of my hand as I was turning around, and sure enough, the facade 'popped' off and fell to the ground. It wasn't broken, and I snapped it back on easily. FYI, I have no cracks in any of my handles that some have reported. The force was pretty hard (didn't feel so good using back of my hand as a mallet), but I think the 'snap-on' nature of the door handle facades may leave them susceptible to popping off.
I had a piece of trim mysteriously disappear too. A small triangular window trim piece on the driver's side near the rear view mirror. Dealer had the part in 24 hours and the install took 15 minutes.
I suspect the dealership lost the piece while repairing the broken charge port locking mechanism as the missing piece was right above the port. But they replaced it quickly and easily.