If you imported an Artemis Demo, and you have a different logo on the front page, this means that a custom logo is set for your front page. Artemis theme offers this option, to set a different logo for an individual page. In this case you also need to remove the logo that is set for the home page.
To do this, please go to your Home page, edit the page, and navigate under the content area, to the Page Settings meta box. There, simply click on Remove Image and Save the page.