If I understand you correctly you want a tool or something to show you where there is a reference made to the wrong index page. A nice tool that I use to find broken links is called Xenu Link Sleuth. It is a free download and its very useful for tasks like this.
I understand now exaclty what you are asking. The easiest solution that I can think of is a 301 (Moved Permanently) Redirect. This can be accomplished in many ways and will preserve your placement in the search engine results.
If you using linux hosting then I would recommend using Apache's mod_rewrite function to do this. If you cant access it then you can use PHP.
If you are using windows hosting then you can also do this with ASP.
While a 301 redirect is the best thing to do in this instance, if you want to find out who is linking to a specific page of your site rather than the domain use Yahoo's site explorer, or Link: command for that specific URL (page included)