Your 'Non-existant Sans' can be rendered with @font-face in your css.
http://www.w3schools.com/cssref/css3_pr_font-face_rule.asp
I don't know of a way to detect font rendering, so I don't technically answer your question. I did find this: http://webdesignerwall.com/tutorials/css3-font-face-design-guide
it's a javascript called Modernizr that ensures if a browser doesn't support @font-face then it will load fallback fonts such as Arial and Helvetica.
