And you'll almost certainly get the same range of answers here.
1) "Worthless, don't bother"
2) "Fairly light, keeps the engine compartment cleaner, improves aerodynamics, and saves my wheelwell liners from getting chewed up. Why would I not keep it as originally designed?"
3) "Only a thick aluminum (Thor/DieselGeek) aftermarket plate makes sense since I don't want to lose my oil pan when I run over road debris."
I fall in the #2 category.
Odds are yours fell off because the proper fasteners were not installed in the proper holes: 6 mm nut and black dowel pins at the front, silver dowel pins (with rubber washer retainers) at the rear, plastic pins in the wheelwells. And you need to periodically replace the little retainer clips (they fit into the pan itself) that the wheelwell pins grab onto.