Gary, the domain has a private registration and I can't see who controls it, so my first question would be do you technically own the domain, or does the developer? Next, do you have admin rights to where the site is hosted?
The primary thing is that you have control of the domain registration. With that, it's easy to make a copy of the site, move you to another host, and point your domain name to the new server.
I know lawn & landscape marketing, branding, and web strategy. I'm not anonymous, I just don't self-promote.