The whole reason of why not use Auto Return makes no sense. He says that if he return without knowing how to reach that catacomb the guild will roast him. Then just use the second level of your skill, Auto Travel, to go there and letting someone of the guild follow him when you will be asked.
People know that he has an auto travel ability (certainly is first level is public knowledge, not clear about the second but even revealing it wouldn't be that bad).