What's the name of the part I ruined?

[dmcutter]

I was in Asheville a couple weeks ago visiting my dad and took a little side trip, ending up going up a steep gravel driveway to look at a log cabin. After a couple of awful, loud grinding noises going over some humps (do NOT try to offroad a lowered Box, d'oh) I decided to walk the rest of the way, but unfortunately had to come back down over the same humps. Last night my wife noticed, as I was pulling into the driveway, that something was hanging down from underneath the front end. Sure enough, I had torn lose part of the plastic piece extending back from underneath the bumper and had put a fairly good sized dent in what I guess is an aluminum or steel bash plate under the front end. So when I call my local dealership tomorrow to make an appointment, what is that actually called that will have to be replaced at great expense? Luckily my comprehensive deductible is only $250. Don't reckon that kind of repair would be done under warranty, would it?