Hello & Welcome to JustAnswer.
Thank you for your question. I will do my best to assist you. My name is Jamie.
The trick is to right-click on one of the other panel headers, e.g. Tone Curve, and you'll see a context menu allowing you ro reselect the Basic Panel.
Alternatively, when in the Develop Module simply do Ctrl+1 (Cmd+1 on a Mac), or in the menu bar go to Window>Panels>Basic Panel.
Did that work for you?