If this is an FT8 QSO we're talking about, there are a couple of files on WSJT-x that will still have the information.
If you have automatic uploads from HRD Log to QRZ.com, ClubLog, etc. can get info from there.
If you're using MariaDB with HRD Log instead of the default option of Microsoft Access then there might be something in the history to help.
73 & GL