Ontological argument parallel

In "God is Not Great" by Hitchens:

"Are there dragons?" she asked. I said that there were not. "Have there ever been?" I said all the evidence was to the contrary. "But if there is a word dragon," she said, "then once there must have been dragons."

He points out that this passage is a fairly parallel argument to that made by Augustine in his argument for god:

1. God is the greatest imaginable being.
2. All else being equal, a being or entity that exists is greater than one that doesn't.
3. Therefore, God exists.

(from Iron Chariots wiki)