When you buy a domain name & website package from certain places (I'm thinking of Yahoo/Geocities),
you have to give your name, address, telephone number etc., for the 'whois'
but for a small fee added to the monthly domain/website bill, you can have your domain details remain
private.
From my understanding that means your information is still listed at 'whois' but it can't be seen by the general public.
I don't know if any other place is like that,
so I don't know if you'd be able to find out.
Good luck. I hope you find out what you want to know.