Yeah, I think that makes sense. Fortunately, none of my seat belts are loose, and I also checked that all the seat adjustments are working fine... I was quite worried about safety when I saw that part under my seat.
Fwiw, I only bothered to check under my seat when I heard something rolling on the floor while I was taking a few corners quickly for fun.
But now that you mention it, upon closer inspection, I did find what seems to be evidence of bits broken off:
Which is kind of odd, because it is heavy (I guess, due to the bolt) and it doesn't look like the two points above are strong enough to hold it anyways. But I'm no mechanic...
I did put my head down on the floor and compared against the passenger seat, but I couldn't nothing obvious. Maybe it is just something left behind by people in the factory or those who have worked on my car.