Once something is posted online, it can remain public virtually forever. It’s important to understand how that works and take steps to protect yourself where needed.
While getting someone’s name and address from their IP address is technically possible, it’s also typically difficult and requires involving law enforcement.
The site you’re used to visiting has simply gone away. Tracking down the owner might not be easy to do.
There is little that you or I can do when a website goes away except to use online tools to try to trace it, or find some other way to replicate the service.