If the layers panel is missing just go to Window then Layers or press F7. If there are still any problems, you can go to the top menu bar and look for the drop-down menu with the list of WorkSpaces. In this case, Essentials is the Work Space used so you will see Essentials at the top. Click essential and the drop-down menu will appear, go to Reset Essentials. This will reset the Essentials Workspace to the default and all the windows that were there will reappear.