IntersectionObserver - how to detect a deleted

Question

In my .js script, I need to implement functionality that re-adds a div to a page if a user deletes it by hand, like if they select "Edit as HTML" and just delete a div from the DOM.

I did some research about setting up observers with IntersectionObserver API, and they work great with changed visibility, changes in colors etc. However, in my case that is not applicable because if i delete the whole div, then the observer is becoming useless.

So far I have this code which works for scrolling up / down with respect to an element, but if i delete the element it becomes useless.

window.addEventListener("load", (event) => {            
    boxElement = document.getElementById("notification_popup"); console.log(boxElement);
    createObserver();
}, false);
function createObserver() {
    let observer;

    let options = {
        root: null,
        rootMargin: "0px",
        threshold: buildThresholdList()
    };

    observer = new IntersectionObserver(handleIntersect, options);
    observer.observe(boxElement);
}
function buildThresholdList() {
    let thresholds = [];
    let numSteps = 20;

    for (let i = 1.0; i <= numSteps; i++) {
        let ratio = i / numSteps;
        thresholds.push(ratio);
    }

    thresholds.push(0);
    return thresholds;
}
function handleIntersect(entries, observer) {
    entries.forEach((entry) => {
        if (entry.intersectionRatio > prevRatio) {

             entry.target.style.backgroundColor = increasingColor.replace("ratio", entry.intersectionRatio);    console.log("higher detected"); 
    


        } else {


    console.log( document.getElementById("notification_popup") == null ); 

    if(document.getElementById("notification_popup") == null){
        var para = document.createElement("P");                       // Create a <p> node
var t = document.createTextNode("This is a paragraph.");      // Create a text node
para.appendChild(t);                                          // Append the text to <p>
document.body.appendChild(para);
    
    } 

Any ideas about how i can change my code, or re-write it to be able to detect a delete event?

Please note that i cannot use jQuery in this case, vanilla JS only.

Thanks!