I wonder how he contacted his colleague. In this case, I presume that routing to other networks were unaffected. But in the general case, with a future of everything over IP, what will network engineers use to communicate about faults?
But in this case the problem was bad routes. You can certainly force your own routers to use fixed routes instead, but that doesn't help you unless everybody else along the path also does it. So it's not easy. There are tricks one can play -- like advertising your network as a set of smaller, more-specific networks (since routers will usually favor more-specific routes over more general ones).
NB Cannot reply under his post
At some point we might see most of the VoIP being transported across the internet as well, but that'll be the far future.