Here are some possible explanations:
* You might be thinking of a different character: Anne's diary details the lives of her family and the other occupants of the Secret Annex. It's possible you're thinking of someone else, like:
* Mr. Dussel: He was a dentist who shared the Secret Annex with the Franks and van Daans.
* Peter van Daan: He was Anne's teenage love interest and the son of the van Daans.
* Mr. Kraler: The man who helped the Franks hide in the Secret Annex.
* You might be thinking of a character from a play or movie adaptation: Adaptations of Anne Frank's diary sometimes add or expand on characters to fit the medium. It's possible the character "Joseph Cohen" exists in a play or film, but not in the original diary.
To help me understand who you are thinking of, can you provide more context or details?
For example:
* What is the character's role in the story?
* What is their relationship to Anne or the other characters?
* Where did you hear about this character?
This will help me clarify your question and give you a more accurate answer.