Downloaded a file in writer and the document I was working on is gone

I was typing a research paper on a new document and finished. I tried to add page numbers to the header, but couldn’t find a way to get the page numbers to start from the 2nd page (the first page being the title page). I found a response here and downloaded an example file. I opened it assuming it would open a new window in LibreOffice, but instead it “took over” the window I typed in. Now my paper is gone and I don’t see any way to get it back. I was planning on saving when I got the page numbers in, so I don’t have a save copy, and undo doesn’t do anything.

Perhaps the new document window simply covered the one you are working on. Check the menu option Window and see if it lists multiple files,

Nope, tried that already. The only windows open are the other documents I had open beforehand.

What about browsing open windows with Alt + Tab or Win + Tab?

Sorry, same result