What does it mean when instead of a specific website, you get their hosting domain?

I am trying to retrieve research material from a particular site. The site has been bought by another organisation. People have been given until a time in January to remove their data. Yesterday, I could not access my data at all (major scare) and today, it was there for about three minutes (giving me a great sense of relief) and then suddenly, the site disappeared and now I just get the site of the domain the site was hosted on (even greater major scare!).

What is this likely to mean? I have no idea how domains work. Could the site just be down or could it be more ominous than that? I know I am asking for crystal ball responses here but someone who knows about domains and how they work might be able to provide some form of general explanation.