Have you gone into Finale's Window menu and checked Advanced Tools Pallet?

there is no Advanced Tools Pallet in the Windows menu.

The graphics tool has suddenly appeared after moving the pallet around on the page.

I suspect that you can get the Graphics Tool icon back by resizing the palette (grab the lower right corner).

However, I suspect that you have already tried that, to no avail, right?

In that case “Reset All Preferences”, and the Graphics Tool icon should come back.

(Another option is the Tools menu where you can switch to any tool from the Main Tool Palette)