Holley issue

On holley`s blown view file they show a little cap/plug? listed #129 as secondary bowl vent valve, but hard to discern where it goes?
I`ve had this carb apart, just primary float bowl and put back to stock, messing with jets.
I`ve had it upside down draining gas out etc.
Later I found a small chrome?/shiny ball, little larger than a bb, under the car, and I could`nt figure where the heck it came from. I was wondering check ball? but holley tech says no way a check ball can fall out of this model carb... ?
https://documents.holley.com/techlibrary_4150_4160_exploded_view.pdf