Loans in Reckon Accounts are saved as a separate file, .LMR. This does not get combined with your backup file. .LMR files are located in the same location as your QBW file. To try retrieve the loan, please try below steps.
Search your computer for *.lmr, if you can see multiple files, see if you can find one with the biggest size and latest date modified.
Replace the LMR file at your file location (the blank loan) with the one that you found above.
Then try to check your loan again.