I assume they updated..... Beside the wrong bank code and the checks appearing in the wrong bank rec bank, and the wrong GL account being hit, what else needs to be corrected?? Personally I would go with a JE reclass to fix the ledger. If they want the bank rec fixed, fix that manually or find someone with PVX chops to write a quick fix.
How did you make the back up? Copy and paste? Why not rename ""bad"" folder and rename the backup folder? That works for me. If the backup was the TST company, copy the live copy to the TST company (GL only so the backup TST PR is not affected) then copy the TST (GL and PR) back to the live company.
And does this fall under the premium STUPID billing rate?