There was a mardi gras type mask in a recent rental I had from an HLE. It did not look like one of those really cheap ones, so I mentioned it when I returned it. It was in plain sight on the back deck, but up against the headrest so it was easy to miss, if I was not putting gas in it I never would have noticed it.

I mentioned it when I returned the car, and they went nuts saying the woman has been stopping in since Halloween looking for it. The car had come and gone many times, but it was in just that one blind spot.

So don't give up hope, it may just be in a dark corner, pushed in by a bag or something, and may show up. Of course it's also possible a bad employee or the next renter is enjoying their new camera too.