If you are using session cookies for cPanel logins, then deletions probably won't show up in the access_log file for cPanel. You can see people visiting MySQL databases area itself in the log, but not when they remove something there typically due to the cpsess entries obfuscating the action taken.
Try "grep cpuser /usr/local/cpanel/logs/access_log" where cpuser is the username of the relevant cPanel account. As Tristan said, you might not necessarily be able to see the actual delete command but it should give you an idea of who was looking at the databases page at the time.