Tried using http://www.opensiteexplorer.org/? It has inbound linking functionality.
Alternatively, I'm not entirely sure if this will work, but try going to Google and putting in:
allintext:example.com/page OR intext:example.com
I tried this to find who was linking to our old domain and managed to find a fair few results. If your client ONLY has the home page now, I'm assuming any other page would be "broken"?
References:
- http://www.googleguide.com/advanced_operators.html#allintext
- http://www.googleguide.com/advanced_operators.html#intext
Hope that helps!