If you lift up the small A/C vent covers next to the A pillars (small windows near the front windsheid) these look similar to the vent outlet tube end that seals against the vent cover. Just a guess.
<div class='quotetop'>QUOTE(bugmenot @ Dec 29 2006, 08:12 PM) [snapback]368419[/snapback]</div> It is a seal that just plugs into two similer openings under the car, just in front of the rear wheels, about 4-5" towards the center of the car.
That notion was already mentioned, and it's definitely not one of those seals. Look at the other pictures and you'll see for yourself. I'm with the idea that someone who test drove it, or a tech who moved it in the lot left that piece in there by accident and that it's not a Prius part at all. I think the biggest clue is the wear that you mentioned. A beat-up looking piece in a brand new car sounds like somebody lost her non-Prius gromet, and is crying herself to sleep over losing it.
I can produce two more of these. They belong to a Costco car seat. There are two (small) on the seat of the car seat and two (larger) at the shoulders that gilde the car seat harness. They tend to fall out when you take the harness off the carseat to change to the booster seat. They also tend to fall out if you look at the booster seat in the wrong (or right) way! If you like, I will send them to you!