I can see my file but Libre office says it does not exist
Is this a result of clicking on the file in the Recent Files list? If so, perhaps try using File | Open to open the file.
Otherwise, please give a little more detail about what you are doing and any error messages you are receiving.
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The preview images on the starting screen and the entries in the recent files picker as well are persistent. They are not and cannot be updated concerning changes made outside of LibreOffice. A file downloaded to your temp directory e.g. will be deleted by Windows following its own rules. If you move a file to a different location (or delete it) by means of your file manager, LibO won’t know and will not try to know.