The problem is not the date that the notes were written but the fact that your request under the Privacy Act did not get any results. There would have been a computer record of the incident created right when it happened but that was not forthcoming either. That shows that nothing came up. You might have an argument to be made if you had got the computer record but not the notes.
Did you ask when the notes were made during the trial. If not then you cannot ask that in an appeal as it would be new evidence. If you did and the office said they were made shortly thereafter then your argument is that you think the judge shouldn't have believed the testimony and that's a hard argument to have accepted.
Do what you will but I don't see a positive outcome for you.