What does hAtom2Atom do when it can't find an atom:id equivalent?

This document contains two entries. One has an atom:id equivalent, and one does not. Run it through hAtom2Atom and see what happens!

Has an ID

Hello, world.

Posted by hober at at 1 in the morning on April 15th.

Doesn't have an ID

Hello, world.

Posted by hober at at midnight on April 15th.