What am I looking at?

Not sure, but if you lift up your hood, see if it is the small section that covers the brake fluid reservoir near the driver's side next to the windshield wiper cowling. Someone may have removed it and left it laying on top of the cowling, and forgot to reinstall it.

Posted via the PriusChat mobile app.

 

Looks like a plastic cover that mounts to the underside of the hood or in the engine compartment has come loose and is trying to escape. Open your hood and put it back where it belongs. It hasn't traveled very far.

 

That looks like the cover for the brake resevior. Open the hood, and on that side you'll likely
see it can fold over the top of the resevior. The rubber seal might slide in, or have a hold for the
hooks on either side.

 

That would have been info to include.
Whoever worked on it probably got side tracked and forgot to put it back.