Answer:
It is something you will never see again.
What's always coming, but never arrives?
I saw the dead bring forth the living. I saw the living bring forth the dead. What did I see?
What is broken if you say its name?
The buyer doesn’t want it, the producer doesn’t need it and the user doesn’t know their using it.
If it’s information you seek, come and see me. If it’s pairs of letters you need, I have consecutively three. What am I?