A best selling self-help book is among the items police say Noah Donohoe had with him when he went missing.
12 Rules For Life: An Antidote to Chaos by outspoken Canadian psychologist Jordan B Peterson received global attention in 2018 for its provocative and informal style.
Aimed at young men, it provides life advice using a mixture of personal anecdotes, religion and mythology.
The rules include: Stand up straight with your shoulders back, treat yourself like someone you are responsible for helping, make friends with those who want the best for you and pet a cat when you see one on the street.
Peterson has often attracted controversy for attacking liberal views on issues like transgender rights.
Although many commentators describe him as right wing, he has defined himself as a "classic British liberal".