Hi, I had the same issue and the site logo is not visible on a desktop browser either apparently when not logged into WordPress. As on my end, I noticed that the logo css style was set to display:none for some reason.
#site-logo a img.standard-logo {display: none;}
So to counter this, I placed the following in Theme Options > Custom CSS and the logo displays as expected:
#site-logo a img.standard-logo {display: block;}
Give it a try and hope this helps!
Frank