I received robot inactive alert and when checked, I found that robot.cfg does not exist in the system.
Did anyone faced this issue in their environment?
Yes. Happens more often than infrequently in my environment.
Usually the cause can be tied to a failure of the robot to write the updated .cfg file. Seems that the code doesn't pay much attention to the success of the steps necessary to rewrite the cfg file when the robot is updated or restarted and so if you have a full disk or a permissions issue it goes away.
There's also a defect where sections of a cfg file will be dropped. Usually I see that manifest itself by dropping one or more sections out of the cfg file but not losing the entire contents. This is supposed to be fixed in the latest robot version but I've not seen that to be true.