Whitecrow;
Using the IP will work on most sites with both a dedicated, and exclusive IP.
For instance
http://64.233.187.99/ will get you to Google.
or
http://66.116.195.67/ will get you to my site.
Many hosts, however stack several sites upon one IP. known as Virtual hosting, this requires a functioning DNS server to distinguish which of many sites you are looking for on that IP
Another method that might have the effect youl saw just occurred to me:
If the govt, or some agent thereof, placed a list of false IP/domain name registrations into the DNS system, then withdrew them a few hours later, the bad addresses would propogate thru the system for a while, and then, once withdrawn, might then be "straightened out". DNS servers are not my thing really, so that is a S.W.A.G., at best, but possible.
Of course this would probably be a crime of some sort, but I wouldn't hold my breath for a DOJ investigation.
Fred