Help! '08 Prius - what is this part called?

On my recent road trip (photo of car w rack, box, and bike on roof in mountains coming...) I managed to hit the front underside of my 2008 Prius against something, knocking a plastic guard/plate loose. It is a rectangular piece of plastic that is secured to the very bottom of the car, directly behind the front bumper. It is secured by 5 bolts across the front (I did not see bolts in the back, but it is possible that there are some and i just don't see them). As best I can guesstimate, it seems to be about 7" wide by about 4' long.

When I hit whatever it was, one of the bolts on the corner came loose and dropped, and the plastic piece chipped; hence the necessity for a new piece and a new bolt.

I want to buy a new piece and just put it on myself and avoid the expense of going to a shop, but first I need to know what the name and/or part number is of the piece I am looking for, as well as the bolt. Even an illustration somewhere of the pieces underneath the 2008 Prius would help....Thanks for any help or guidance you can give!

 

Thank you! I have the part on order.