Elements hidden by the Hide On Device feature aren't gone forever; at any time, you can see all of the hidden widgets on a page by clicking the Unhide Elements button at the bottom of the left menu.
Click the Unhide Elements button.
Hidden elements are now displayed.
Once hidden elements are displayed, you can restore hidden elements by clicking on them. A pop-up will display prompting you to restore the element.
Things to consider
Unhiding an element isn't revealing my image
If you are using the unhide element feature and it's not revealing the image on your Site, your image might need to be re-added and uploaded.