Did you edit the theme files directly? That should be avoided, because if you edit the theme files directly, your changes will be overwritten every time the theme is updated to the latest version.
If you used CSS to add your icons, an easy way to add custom CSS and not worry about it being overwritten when the theme is updated is to install the Jetpack plugin and activate the Custom CSS module. You’ll then add your custom CSS in the new stylesheet editor that’ll appear in your dashboard, under Appearance > Edit CSS.
As alternatives, you could either install a standalone custom CSS plugin, or create a child theme. A child theme is also the route to go if you made the edit within the theme’s PHP files instead of using CSS. Here are some more guides in case you haven’t made one before:
http://op111.net/53/
