After domain name change attempt website went back to original theme design

Hello,
I (stupidly!) changed the Site Address (URL) and WordPress Address (URL) in General Settings, and got 404 and couldn’t login to admin panel any more

I then figured out that adding two lines below to wp-config.php would bring my site back to old url
define(‘WP_HOME’,’https://example.com’);
define(‘WP_SITEURL’,’https://example.com’);

My site is working and I can login to admin panel, but it went back to original theme design (I’m using BlankSlate) and my custom adjustments are gone..
Is there a way to recover it? I don’t have a backup before the I changed URL’s and the programmer who helped me out to tweak the theme is not available.

Thanks in advance!