OMG, you're right. Of course the protag will want to stay on board and travel along with the space ship.
You've helped me figure out the ending!
I hadn't decided if he would actually meet the owner of the ship, his hero ? a Flash Gordon/Buck Rogers type of hero ? and he will ask to stay on board, and even make a very good case. But the owner will turn him down this time.
This whole story is a bit of back story for another story that I've already written a first draft of, which ends with the orphan character, as an adult (early twenties) getting to travel along on the ship in the end.