It was likely just in the bag with the Volquartsen parts. There are 2 common slave pins - 1)for the trigger/disconnector, and 2) for the old style hammer/shims alignment. You don't actaully need any of them, but they're handy. I find I use mine for the trigger assembly on every trigger job, so I just keep it in a safe place.
Since you've already installed the new springs I would just leave them in and keep the originals as spares.
Now that your trigger is back together and you inderstand it's inner workings better, give yourself a big pat on the back for a job well done. There's a lot of pride in doing a good job on something most folks shy away from.