I can see the issue on your site, it makes no sense though since the JS file is clearly there in the source. That being said, I can't replicate the issue anywhere else.
What cacher are you using? Filecache, XCache, APC etc.
Just a follow up, I believe I found the cause of the issue. I had added async in the headerinclude template to one of the javascript calls, and I think that was the issue. )