such a thing as void OnSetActive (false)?

I did one level having enemies as prefabs and respawned them as needed. But level two I decided to just set the dead enemies SetActive (false). I like it better because with prefabs I found myself having to prefab their waypoints and anything else that their scripts referenced. A slippery slope. Problem is....that when I kill an enemy, setActive (false) and instantiate his ragdoll, when I set him active again ( respawn) he is still in his attack mode - or whatever mode he was in when he died which is usually attack mode. I tried putting code in his healthscript so when it hit<1 he would reset to patrol mode,I tried a script on the prefab ragdoll and other places to access that attack script to reset it but nothing takes - he respawns in attack mode. I even tried OnEnable and OnDisable but nothing seems to work. so...is there a way to say if(GameObject.activeInHierarchy == false) to DoSomething. I tried that as well on another active gameobject. but nothing takes.below is the code how I envision it should work - placed on an active gameobject accessing the public static variable of the enemies MaxDist.When he is attacking me it bumps up to 25 from 15 ( patrol). and when he respawns he starts at 25

 using UnityEngine;
 using System.Collections;
 
 public class resetRobotOne : MonoBehaviour {
 
     public GameObject enemy;
     MonoBehaviour MaxDist;
     void Start () {
         MaxDist = enemy.GetComponent<robotAttack>();
     }
     
     
     void Update () {
         if (enemy.activeInHierarchy == false)
             robotAttack.MaxDist = 14;
     }
 }