Although Ralston is trapped, why does he find it important to keep track of his bicycle lock key?

When Ralston slips his bike lock key into a little hole near his feet, he states that it is important to get it in case he ever gets out of the canyon. Getting to his bike lock key is a side challenge that allows him to take his mind off of the bigger problem, the chockstone pinning his arm. It's a tedious but smaller challenge.