Using Backup and Migrate, I created a mysql file from my live site and tried to restore in on my local system. Nothing happened - no restore, no error message and no log messages. It turned out that my max file size was set to 8MB and the mysql file was 9.4MB. After updating the .htaccess and php.ini files to increase the max file size, the restore worked fine.
So, my request is to please add an error or log message when the restore fails because the mysql file exceeds the max file size.