I was fired, however, I never had a right up

I was recently fired and never given a write-up from my former employer. To back up this claim, I have supporting evidence, although I am no longer in contact with the former employer. There are no witnesses who can corroborate my story. I am looking for a freelancer to assist me with finding out what I should do in this situation. If you are able to help me, please let me know as soon as possible. Thank you!