What The Heck Is This and Where Does It Go?

Hey Everyone -
After getting back from taking my kid to school this morning, I looked down on the carpet under the driver side – and found these four pieces. A quick cursory glance under the dashboard did not show me where this might have come from.

I'm not sure how important it is but I would love to know what it is and where it goes so that I can replace it if necessary. It looks to be a washer of some kind but like I said, I have no idea where it used to call home.

I know it is not the rubber brake button because that failed on me about four months ago and I have since replaced it and the new one is intact.

I have got a 2005 Tundra double cab, Ltd, with the 4.7L.
I appreciate in advance any thoughts and insights.

 

Any chance it could be from something like a seat rail?

 

I don't know because I didn't look under there. It was multiple pieces like it had hit the firewall and tumble down to come to rest. I'll check under the seat and the seat rail itself.
Thanks for the suggestion.

 

The plastic stoppers on the seat belt? Button of a shirt?

 

Communion wafer