I Am Christian

Creationists like to characterize the athiest worldview as "Nothing happened to nothing for a long time until it became everything".
They like to use this description to show how silly that idea is.
Let's move right on by the fact that they accept an eternal, omnipotent sentience that has always existed and examine the concept of nothing.

What makes creationists think that an atheist believes there was nothing?
Whoever decided that nothing is the default state which something must replace?
What reason do we have to suppose that nothing ever existed.
Has anyone ever observed nothing? Is there any proof that nothing is even possible?