Sadly, quite nothing to do, see:
22 pages term paper replaced with pound signs.The file seems indeed empty.
Check the temporary folder of the system (see in OOo Tools>Options>OOo>Paths). If there are folders like sgmlf.tmp with a file having the same name inside, make a copy of that file, rename it in .odt and cross your fingers. If you have not rebooted, you might have those files still there.
LibreOffice 7.0.3 on Xubuntu 20.10 and LibreOffice 6.4.6 (portable) on Windows 10.