Hello,
I was replacing the trunk opening button on the trunk lid.
After I removed the 4 nuts holding the plastic chrome piece containing the trunk button and license tag lights, I was doing some clean up. Then, this nut fell out of the inside of the trunk lid.
I couldn't find where it belongs.
Any ideas?

 

Looks like a 'not-yet-installed-rivnut'?

Maybe look for the hole if came out of?

 

Hard to tell from the pic. Almost reminds me of the brass threaded inserts that the coil cover bolts screw into…

 

The boot panels have them installed for CD changer as well as other bolt in brackets for optional accessories.

 

Mystery solved!
Being the dumb-*** that I am, after looking all over inside the trunk lid for a possible location for the nut, I discovered, while putting the inside trim cover back, that it fastens the grab strap under the deck lid.