Hi and welcome to the forum!
Sadly, quite nothing to do I fear, see:
22 pages term paper replaced with pound signs.What Operating System BTW?
Check the temporary folder of the system (see in OO Tools>Options>OO>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.
It often happens when there is a power cut or a crash when saving.
If you want to help fix this problem, you can also do this survey created for this very problem:
Document Recovery Survey.
LibreOffice 7.0.3 on Xubuntu 20.10 and LibreOffice 6.4.6 (portable) on Windows 10.