If there is a way to recover a deleted Watch List item, I have not heard of it.
If the item was in the last hundred or so most recently viewed items, you can check your Recently Viewed list to see if the item is listed there.
If you have your Watch List already open in a browser tab on another device, you might be able to see an old item, but if you refresh the page or navigate to page two any old items will disappear.
You might be able to recreate the search you used to find the original item using the same device and browser you originally used if you have not cleared your browser history.
