If you use “Insert by URL” the image is loaded from whatever URL your provide. It is not uploaded to your server at all, nor is any information added to the postmeta
table as far as I can tell. It seems to be equivalent to simple hand-writing the HTML
into the post body.
You can pretty much work this out by looking at the page source, but I also tried to search the database of evidence just in case. I did not find any.