Change the domain to "try" and my site disappear… HELP!

So I’ve been redesigning this site for the last 6 months. It’s almos done. It is a new look to an existing site, which is still live on its original domain.

For this new site and unlike the original, I’m working on WordPress. The site is now pretty much ready and a week ago I changed the domain on the Dashboard to “try.” Next thing I knew, I was looking at the old site and the new one disappeared.

From that moment I haven’t been able to log back on the WordPress dashboard and the domain I was working under, shows the menu but not the theme of the new site.

I have no access to the Server myself and I have no clue how to reverse this issue.
Is my new site gone? (I really hope it’s not).
How could I solve this?