Iirc he went to an audition with a hairpiece but Roddenberry was totally against it. In that his future wouldn't have someone who would want to hide their baldness
From what I've read Roddenberry wanted someone with hair, so they tried to compromise with a hairpiece, but Roddenberry thought the hairpiece looked bad and preferred him without the hairpiece and was talked into Patrick Stewart anyway.
I thought Stewart said in an interview that he actually had/could grow hair back then, said so in his first audition, and the directors just preferred him without it?