The jewel is symbolic of the dormant Buddha Nature in him. Only once he sees his friend again does he learn that he has a jewel with him.
In Mahayana thinking, each person has the potential to be enlightened in this lifetime, if they can only realize that.
The Buddha Nature (bodhicitta) is what we call that hidden potential for a person to become a Buddha.
Once the person starts to realize that they too can become a Buddha, then the bodhicitta will start to develop into eventual Buddhahood, if that person follows the Dharma.