THIS IS THE ANSWER. I had the same issue, found the answer on a different forum. Follow the instructons below.
Look to see if it has somehow ended up below the text area in the editor. If it is, click on the "screen options" tab at upper right and make sure that under "Screen Layout" that "Number of Columns:" is set to 2. If it was set to one, then you will need to drag the publish section from below the text area up and to the right of the editor window.
If the details of the PUBLISH module do not show, just click the word publish in the module title blue color and the details of save draft, edit, publish will appear. Then you can just drag that back to the 2 column format.