Ok for whois.domaintools.com, nice. I used http://whois.ws/whois-net/pdadb.net/ which has the new IP address.
Many servers bloc access with ip address because they can host several sites. Maybe on the same server, at the same ip adress there are pdadb.net, something.com, azerty.net ...
So the only way to view the site you want is to type domain name because the ip address can't make the difference.
Just remember to remove this fix when the site is back, because if the IP address or domain name is modified it will not work anymore.