Remove "Search for" in search bar widget

Hi! I continue to love the Frontier theme. Thanks! I was looking for how to remove the “Search for” text that appears above the search bar in the widget. I have found some of the formatting options in the style sheet. But, I cannot locate the text. I know it’s part of a span class. Is the text in a .php file? If so, where? I was looking for a search.php but could not find one…..