Default Top image disappeared

I somehow managed to delete the default main image of the theme.. or it disappeared, and im not sure what I did to make it go away, or how to get it back.. When I downloaded the theme, I loved the default image (Lake Moraine, Banff), but as i was setting up my site, i knew I would want to change that image to one of my photos at some point in time, but at some point in time, that default image disappeared completely, and i cant figure out how to get it back, much less how to change it. It disappeared about the same time I added the “Limb Gallery” lightbox that shows the thumbnails in the Banner widget, but even after I added that widget, the main photo showed for a while, before it disappeared, and Ive tried deleting that widget, and the main photo does not come back… How do i get that large, full width photo to come back, and how do i change that image, once i do??

The page I need help with: [log in to see the link]