Answer:
Once you know it exists, it no longer exists. What is it?
The buyer doesn’t want it, the producer doesn’t need it and the user doesn’t know their using it.
What time is spelled the same forwards and backwards?
Without this, H2O would just be 2O
What is in seasons, seconds, centuries, and minutes, but not in decades, years, or days?
I touch the Earth, I touch the sky, but if I touch you, you’ll likely die. What am I?