Please use the Question Tags to state which Twine compiler / application you are using to create your Story HTML files, as answers can vary based on that information. I will assume you are using the Twine 2 application.
The Import From File option can (re)create a Story Project from either an Archive HTML file or a Story HTML file.
You state you have "saved the game file", if that means that you used the Publish to File option to create a Story HTML file then you can import that file to recreate the missing Story Project.