I used a plugin that hides wp-admin and does a lot of other things, but it hid wp-admin for admin-user too (due to some bad settings on my part probably) - how to revert back? I deleted the plugin's folder to get back to wp-admin, but as soon as I activate it, it again starts hiding admin-stuff. (It's retaining the settings it seems, because it doesn't hide admin-panel right away upon activation on fresh install. I had to alter the settings in wp-admin to make it hide wp-admin.)
I usually dont use plugins for this due to the fact its unstable.
I use this in my theme functions.php so you can always remove it if need be and it saves nothing to the DB.
This also leave open the admin ajax files if you need them for any theme functions like thickbox and a few others.
You said you deleted the plugin folder ... so login to your website via FTP and look for your .htaccess file
This probably was changed by the plugin and re-writes the URLs like
Check / change the code back to: