Did you perhaps have the previous printer's software create the "save to" folder for scanned documents during it's installation and then never moved the documents elsewhere?
And then perhaps uninstalled the old printer software before installing the new printer's software? This process would have deleted all "old printer" associated folders, including the "save-to" folder and contents.
If so file recovery is the only bet, hoping that the drive activity since the uninstall did not overwrite what you want to retrieve.