Tamiya WRC Poly cap missing?

I am building my first model car - a Tamiya 2001 WRC. Step 2 says I need poly caps, but I can't find them in the box. Are they somewhere in there or do I buy them separately? What are they for, anyway?

They should be in a little bag along with the wheels or tires or some odd detail parts. Sometimes they get lost inside a tire or something. I don't think I've ever had a missing Tamiya part ever. And only once a defective part.

I've only had missing parts after I open the box. :(