You can restore the bookmark toolbar by pushing alt+v (opens the view menu) -> toolbars -> Bookmarks Toolbar.

Here's a page with step-by-step instructions demonstrating another way to toggle it: https://support.mozilla.org/en-US/kb/bookmarks-toolbar-display-favorite-websites

Note that Firefox 52.6.0 ESR is current (released alongside with Firefox 58).

You may have to visit a bookmark and open the link in a tab to make Firefox retrieve the favicon if that is what you are missing.

If you do not see any bookmarks on the Bookmarks Toolbar then check if "Bookmarks Toolbar Items" is on the Bookmarks Toolbar.

Open the Customize window and set what toolbars (Show/Hide Toolbars) and toolbar items to display.

• Right-click empty toolbar area -> Customize
• "3-bar" menu button -> Customize
• View -> Toolbars
  *you can tap the Alt key or press the F10 key to show the hidden Menu Bar temporarily

• check that "Bookmarks Toolbar Items" is on the Bookmarks Toolbar
• if "Bookmarks Toolbar Items" is not on the Bookmarks Toolbar then drag it back from the Customize palette to the Customize window to the Bookmarks Toolbar

• if missing items are in the Customize palette then drag them back from the Customize window to the toolbar
• if you do not see an item on a toolbar and in the Customize palette then click the Restore Defaults button in the Customize palette window to restore the default toolbar set.

• https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars
• https://support.mozilla.org/en-US/kb/navigation-buttons-missing