need help with missing/broken body piece

Pharmacist

I was inspecting my brakes today and by coincidence I noticed a missing piece. The piece is a small shelf-like cuboid piece of rubber just in front of the rear brake caliper. Here is a pic of the missing piece on the driver side:



Here's a pic of the piece from the passenger side, the way it's supposed to be:





Here is where it broke off. The piece actually extends from the wheel well into the undercarriage where there are 2 bolts holding it. It forms what appears to be a small air dam or something. My finger is pointing to where it broke in half.



Here's where it continues underneath the car



What is the function of this piece? Is it important? And how would it break off like this? I don't recall running over anything. And where would I get the part # to order such a thing?

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2009 370z Sport Touring/Nismo shift Knob/Z1 motorsports 34 row oil cooler