My host uses mod security. Perhaps they changed a setting that would hinder this type of activity.
So does mine-- it's an optional add-on-- but when it kicks in, you can see it in the error logs. Generally it's something truly sinister, like asking for nonexistent files with ".exe" at the end.
It's just as likely that the robot simply got bored and went away. The list of robots who hammer away forever, day after day for months and years, is really pretty short. You block IPs because if they allow one robot today, they'll allow an unrelated robot next week.