outpost example from unity 3.x Game dev essentials book

I am working on the example specified in the unity 3.x Game Development Essentials Book. I'm stuck with Chapter 5, Approach 3- Trigger collision detection (Page no 179 from pdf). Approach 1 and 2 worked but 3rd doesn't.

Situation: My outpost is similar to the one in the book except that door is not a direct child of the outpost. The hierarchy is

Outpost > Building> Door.

So the way I trigger the door opening animation is

transform.parent.parent.gameObject.animation.Play(animName); I have the triggerZone applied to outpost and DoorManager to the door.

Problem: The door animation does not work with approach 3.

TriggerZone script looks like

 void OnTriggerEnter(Collider col){
         if(col.gameObject.tag == "Player"){
             if(Inventory.charge == 4){
                 transform.FindChild("building1").FindChild("door").SendMessage("DoorCheck");
 
                 if(GameObject.Find("PowerGUI")){
                     Destroy(GameObject.Find("PowerGUI"));
                     doorLight.color = Color.green;
                 }
 
             }else if(Inventory.charge > 0 && Inventory.charge < 4){
                 textHints.SendMessage("ShowHint","This door won't budge..guess it needs fully charging- maybe more power cells will help...");
                 transform.FindChild("building1").FindChild("door").SendMessage("DoorCheck");
             }else{
                 transform.FindChild("building1").FindChild("door").audio.PlayOneShot(lockedSound);
                 col.gameObject.SendMessage("HUDon");
                 textHints.SendMessage("ShowHint", "This door seems locked.. maybe that generator needs power...");
             }
         }
     }

SendMessage("DoorCheck") successfully calls DoorCheck method in the DoorManager. It also plays the sound (audio.PlayOneShot) but does not play the animation.

 void DoorCheck(){
     if(!doorIsOpen){
         Door(doorOpenSound, true, "dooropen");
     }
 }
 void Door(AudioClip aClip, bool openCheck, string animName){
     audio.PlayOneShot(aClip);
     doorIsOpen = openCheck;
     transform.parent.parent.gameObject.animation.Play(animName);
 
 }

I know the situation is kind of tough to understand because I don't have any errors or warning. The animation which used to work in Approach 1 and 2 does not work in 3. I hope I tried to explain the situation. Please let me know if anybody else had faced the same issue.

I am NOT using unity 3d Pro. I'm using the standard license.

Thanks in advance