Hello there,

Have you clicked on "Restore Defaults" and see if that solves the issue? https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars

Keep us posted.

Firefox definitely includes a little house icon. But it might have moved to an unexpected location. If it's not on any toolbar, and isn't overflowing off the bar (there is a >> icon for buttons that don't fit), and isn't in the collection of unused icons, then as mentioned in the above post, I think the "Restore Defaults" button toward the bottom center of the Customize tab is your best bet.