Wanted: One of the plastic caps that cover a bolt securing the firewall insulating pad (see photos). Wish I knew what it is called; seems (?) to be different than the others as it covers a bolt instead of being a ribbed "push pin". Don't know where this one went.
Thanks!
The missing one:
Click to view attachment
"Push Pin" type?:
Click to view attachment

Never seen one that had a cover.

Oh, maybe it never had one? Otherwise, it must have taken off with the missing oil cap of @Vaccarabite .