How to make object come back

You are turning the renderer off but you aren't deleting the gameobject. You should be able to just call gameObject.GetComponent<Renderer>.enabled = true. Note that disabling the renderer will not disable the trigger with the object, just will make it invisible to the camera.

From your snippet it looks like t$$anonymous$$s script is interacting with some collectible objects, and that you want to re-enable them when some outside event happens, like a special collectible is found. If t$$anonymous$$s is the case, an easy way to accomplish t$$anonymous$$s is to add a script to each collectible:

 public class CollectibleScript : Monobehavior{
     private static List<Renderer> renderers;
 
     void Start(){
         if(renderers == null) renderers = new List<Renderer>(); 
         renderes.add(GetComponent<Renderer>());
     }
 
     public static EnableAllRenderers(){
         foreach(Renderer r in renderers){
              r.enabled = true;
         }
     }
 }

And then when you want to enable the renderers you can simply call CollectibleScript.EnableAllRenderers();