Hi is conduct Unbecoming of an employee considered deflamation

My supervisor wrote a memo regarding incidents over two years ago and i had no knowledge, my union contract states we are to know what's in our files and should bear our signature...the memo was placed in my file, prior i went for a higher position in the company and did not receive it, i think the memo haa to do with why i did not get the job. I feel my employee rights were violated and woeth ethic challenged