I also think that the three days prior to leaving Toronto in which nobody can account for Stephen's whereabouts are a big deal. It indicates to me that when he left home to go to the airport (the first time), he did not plan to return home-- no matter what. When his plans to leave town that day were ruined, he chose not to return to his life until flying out on Monday, but to lay low instead. In my opinion, if this does not indicate that he was purposely leaving his life then it indicates that he was struggling psychologically at this point. If he stayed in a hotel for those three days, that right there would practically eat up the entire $200 cash the authorities say he had with him for his trip.
Furthermore, when traveling internationally I have always been told not to bring any cash! But instead to use a card. You can either use your typical credit card or a pre-loaded traveler's card (easily obtained at AAA). Because there are so many thieves, gypsies, etc who take advantage of tourists and attempt to rob them; I was advised that card is much safer than cash because you can report the theft and any funds spent by the thief will be reimbursed. In my opinion, I would never choose to travel internationally with only cash. Not to mention, $200 is VERY little money when you take into account the hiccups a traveler may encounter. (Taxi rides, boat rides, lodging, meals, possibly medical care, anything really...)
This is all just my opinion and because we do not know much about Stephen's thought process leading up to his disappearance he may have logical explanations for each point I brought up.