I wanted a Ribbon Choker for my avatar, and noticed that it's rarity was "special". I looked it up and found out it's an Cash Shop item.

It's not available at the Cash Shop, but neither is the rarity "retired". Do items like this occasionally come back to stock in the CS, or are they gone for good?

Sometimes they come back. And even the so called 'retired' items of the cash shop tend to show up again XD (i.e. the feral accessory trunk)

Alright, thanks . ^^

According to Keith, nothing on Subeta stays retired forever.