My car has a plastic piece at the front of the rear wheel wells and one of them is dangling by one fastener. I had a 2011 Prius which developed the same problem on both sides and I just removed the parts altogether. It seems strange that I have had this inconvenience with two cars now and I do not see where anyone else has had the same issue.
One of these days I want to have a thread on here about the Prius undercarriage... I understand that lots of MPG improvements can be had by covering the underside of the car in the same way super expensive sports cars are covered. But in the case of a Prius I understand why Toyota doesn't bother, especially considering how many warranty repairs they have to make to what little bellypan system their cars do have. I mean how many people still have their trap door for oil changes? Point being improving aerodynamics under the car is not simple because of making sure the exhaust system doesn't melt anything, as well as making sure covering the underside doesn't increase drag because its done wrong... I've still much to learn about aerodynamics, but hope to soon have a template that people can download. Any thoughts? I'll more formally post this discussion in the future once I feel like I digested all the available knowledge on the subject.
I had the same problem with my 2010, at the first oil change,(5000 miles) the left plastic part was hanging by only the plastic button, the screw was gone. The tec replaced the screw, tightned the other side and went on with the oil change. Some time later, I noticed the right plastic part was gone, and the area inside the remaining left one was packed full of mud. ( I have to drive 2 miles of gravel road.) After considering the possible lower wheel well rusting potential caused by the mudball, I removed the other plastic part . Now that area on both sides stays clean or flushes clean easily with the garden hose.
They are called "Splats" or air deflectors located directly in front of the wheel. They work by modifying the air flow down and around the tire.
I'd love to make a template for full bellypan (minus exhaust area) to improve MPG. And I'd love to build higher quality splats that don't get so beaten up in parking lots... Any ideas on where I can study up on how to do that? Seems like underbody aerodynamic is not simple at all!