My bad, there's little info in the page or the game about how to pick stuff, until today I assumed dropping guns was final and there was no way to pick them, I see now that the `E` key is what I was missing, I assumed `F` was the key since we use it to interact with the vendors, and there's no prompt for the `E` key when sitting on top of the guns or the key card.
I finished the experiment ok now, thanks.