I'm sorry to give you this news 4 days later, but you need to restore the backup that was made at the beginning of the closing process. If the close did not complete properly there will almost certainly be damage to your data.

So will restoring cause any loss of new data since then?

Yes. Restoring a backup will result in losing any work you have done since that backup.

When restoring, you will have two options. You can either overwrite an existing company, or create a new company. If you overwrite your existing company with the backup, all work you have done since that backup was made will be lost completely. I recommend you take the option to create a new company from the backup. That way you will still have the original company so you can tell what needs to be re-entered in the new company.

Be sure to change the name of the old company (Maintain menu > Company Information) so you can tell it apart from the new company.