Omeka gone?

First off: Sorry for my ignorance, I'm far from tech savvy.

I work for a private collector of historic periodicals and we built a website which featured an Omeka database, that database seems to be missing.

Here is my understanding of what has happened: The website and it's content moved to a new domain name, when it moved our web developer did not bring the Omeka portion with it. The old domain expired and apparently is now full of malware (when you try to visit the site your browsers will warn you to not enter)

Does anyone have any suggestions on how we can retrieve the database?

All of that is pretty well outside the scope of what we can address here. That's going to be a question for the web developer who moved the site and domain, or for someone else who has access to the servers involved.