Accidentally drove over curb

[Former_Neon]

Last night, I accidentally drove over a curb (about 5" high) as I pulled into a gas station. The curb juts out into the lot and that's where I encountered it. It didn't scrape the bottom of the bumper or anything, however it did dent that black plastic thing that's bolted to the underside of the front of the car (I have no idea what it's called). If I knew how to attach pictures here, I'd show you.
I'm worried that I might have damaged my Yaris.
I probably hit the curb at about 15-20 km/h. There are no marks on the tires or rim that I can see. There are no leaks either. I just took my car onto the highway today for a quick test-drive and, at 120 km/h (75 mph), there is no shaking or shimmying. The car pulls very, very slightly to the left at high speed, but I don't know if it was like that before or not.
From kneeling down and looking beneath the car, I can't discern anything having been bent (other than the hard, black plastic thing I mentioned).
Do you think I lucked out and it's okay?