I think in this instance it's also a matter of tools. Visual Studio/Visual Assist would have been able to find the class definition, and that's where the comment would go. For cscope it's a matter of configuration, which should be auto-generated by the build tool.

If the class is being used, then the definition has got to be somewhere, hopefully in a header. It's simply a file that is included somewhere. And it will be human readable. There is no magic.