Also you can open and close the list of accounts by clicking the small arrow left to the word Budget in the left panel. So if you have clicked that by accident, it might just be that the list is minimized and when you click that arrow again the list will open up again.
Superbone If I understood correctly what you explained, you were talking about the whole panel, I was not. There is a little toggle next to the word BUDGET (and next to TRACKING if you have tracking accounds) to hide the list of accounts even when the panel is not minimized. I personally use those toggles to have the list of my tracking accounts collapsed most of the time. That's why it came to mind.