I just had my 2008 prius towed out of my driveway this am. I found these in the gravel afterwards. They look to have come off the underside. They are soft pliable rubber. There were tire marks where it looked like it was drug through the gravel. It was towed from the rear as car was facing forward in the driveway. Are they anything to be concerned about? They must have served some function.
look like plugs. maybe where they hooked up the tow cable. hang on to them if you're getting the car back.
I guessed before I even enlarged the picture you posted. Those go into oblong holes on a heavy gauge plate, just inboard of the rear scissor jack bearing points. Look under there and you'll see. I believe they ship-loose from the factory, since on ship or wherever there's locator pins that go into those holes, to prevent the car shifting around. Every so often there's a post here: someone finds that pair of plugs in their glove box (upon delivery of a new car). The dealership is supposed to install them as part of Pre-Delivery Inspection, but sometimes drop the ball.
Pends on how long you plan on keeping the car and/or how much sand, salt, etc might get into the holes....
