No need to be confused, you've probably inadvertently hidden it. The thing is that in every Module, all the individual panels in each of the left and right-hand columns can be optionally shown or hidden under user control (there are few minor exceptions such as the Navigator, but by and large this control is available throughtout Lightroom).
So to bring up the options for each column (in your case the right-hand column of the Develop Module), simply right-click (ctrl-click on Mac) on ANY of the headers that are showing in that column and you'll see a pop-up context menu like the attached screenshot. Here you can see that I've previously hidden the Basic panel, so all I need to do is click on the Basic line and it's restored. Conversely, I can use this method to hide a panel.
