It appears that the access port held up by clips in the plastic shield under the engine compartment of my 2010 flipped down after a recent oil change, scooting along the roadway, like an air scoop for some miles. I thought the noise was from frozen slush that had lodged underneath until I looked and saw the problem. Has this ever happened to anyone before? ALSO, did this scoop up and deflect salt, slush and road grim that could cause problems down the road?
This happen to me, had it fixed under warranty at the time. You should be able to re-attach it with tyraps or something else. Just do a search on PriusChat.
Least expensive replacement; 10 2010 Toyota Prius Lower Engine Cover - Body Mechanical & Trim - Action Crash, Front, Rear - PartsGeek