I can see the document in the Recent Documents but when I try to open it, I get this message “/home/philip/.cache/.fr-KDQwAB/Document 3D.docx does not exist.” I really need this document.
.cache directory is not used by LibreOffice. May be you opened that document directly out of another application (browser, email application, chat tool) which cached the file as long as the specific application was running. Cached data are deleted on exit of the originating application caching the data. And if you see the file in Recent Documents this just supports the assumption, that you (double) clicked the file within another application and this caused your operating system to start LibreOffice in turn. I strongly recommend to never rely on double click a file in another application to start LibreOffice (or the application which is associated with the file extension) without an immediate Save As and to store the file where you want the file to be (and you can remember, where you stored it).
In short words: There is absolutely no hope to recover .cache/.fr-KDQwAB/Document 3D.docx by means of LibreOffice (May be some “Recover deleted files”-tool can do).
If you are under linux and you are using ext3/ext4 as a filesystem you could try extundelete , ext4magic or magicrescue
Hope that helps.
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