You might be in one of two situations you just deleted the thumbnail but did nothing else.
Here’s what to do when you accidentally delete a thumbnail from the New Tab page and want to get it back. Now imagine for a second you accidentally delete a thumbnail? Most of us would think that it will come back because we will continue to visit the website but that sadly is not the case in Chrome. For both Chrome and Firefox, extensions and add-ons exist that let you increase the number of website thumbnails that appear on the new tab page.
Based on your browsing history, you can save up to eight different websites like this. It is an exceptionally useful feature and most browsers have a speed dial functionality. Chrome’s New tab page features a speed dial it has thumbnails of your frequently visited websites and you can click a thumbnail to instantly open the website.
