Domain redirect

Hope someone can help here goes:

I have registered 2 domains pointing to the same hosting service, i.e same index web page using the htaccess file with this entry:

# -FrontPage-
IndexIgnore .htaccess */.??* *~ *# */HEADER* */README* */_vti*
<Limit GET POST>
order deny,allow
deny from all
allow from all
</Limit>
<Limit PUT DELETE>
order deny,allow
deny from all
</Limit>
AuthName mydomain.com.au
AuthUserFile /home/mydomain/public_html/_vti_pvt/service.pwd
AuthGroupFile /home/mydomain/public_html/_vti_pvt/service.grp

Now Im not sure if anythings wrong but curious because i have been indexed with one domain but not the other, my parked domain or subdomain has been indexed not my primary....any reason for this?

Thanks