The ASPNETCDN site examples all have a fallback so nothing should have broken if you followed their examples. It's interesting they did this given others do not.
such as
Production applications should not take a hard dependency on CDN assets. Applications should test for the CDN asset referenced, and use a fallback asset when the CDN is not available.
// Fallback to loading jQuery from a local path if the CDN is unavailable
(window.jQuery || document.write('<script src="/scripts/jquery-1.9.0.min.js"><\/script>'));
