How to fix "ClientRpc call on un-spawned object" error, using UNET

So, I’m working on a multiplayer fps game using the new UNET system, and I’m having issues doing RPC calls. Here is my C# script attached to the player camera:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.Networking;
 public class soldierHandling : NetworkBehaviour {
     RaycastHit hit;    
     [ServerCallback]
     void Update () {
         CheckLookingAt();
         if(!isLocalPlayer){
 
             if(Input.GetKeyUp(KeyCode.E)){
                 RpcPutObjectInHand(hit.transform.gameObject);
             }
         }
     }
     [ClientRpc]
     public void RpcPutObjectInHand (GameObject objectToPickUp){
         Debug.Log("attempting to pick up : " + objectToPickUp);
         if(hit.transform.tag == "equipable"){
             objectToPickUp.transform.SetParent(this.transform.FindChild("holdPoint"));
             objectToPickUp.transform.position = this.transform.FindChild("holdPoint").transform.position;
             objectToPickUp.transform.rotation = this.transform.FindChild("holdPoint").transform.rotation;
             objectToPickUp.GetComponent<Rigidbody>().detectCollisions=false;
             objectToPickUp.GetComponent<Rigidbody>().isKinematic=true;
             objectToPickUp.GetComponent<Rigidbody>().useGravity=false;
             //objectToPickUp
             Debug.Log("picked up : " + objectToPickUp);
         }
     }
     
     void CheckLookingAt(){
         Vector3 fwd = transform.TransformDirection(Vector3.forward);
         if(Physics.Raycast(transform.position,fwd,out hit, 5)){
             //Debug.Log("looking at: " + hit.transform);
         }
     }
 }

Basically, the script checks what the player is looking at, when E is pressed if the object is equipable, its physics are deactivated, and it’s put in the player’s hand. (Yes, I intend to cache etc. this isn’t the finished product)

It works great on the server without the [ClientRpc] tag but obviously, doesn’t call the function on the clients. With the [ClientRpc] tag, the function never gets called and I get the following warning:

ClientRpc call on un-spawned object UnityEngine.Networking.NetworkBehaviour:SendRPCInternal(NetworkWriter, Int32, String) soldierHandling:CallRpcPutObjectInHand(GameObject) soldierHandling:Update() (at Assets/scripts/soldierHandling.cs:15)

I’m confused as the player and weapon are clearly spawned objects. Any help on the issue would be great!