Source Code (what happened to...)

SPOILER ALERT: this is not a review of the movie, it is a discussion of a specific plot point.

I just watched the movie Source Code again and one thing struck me that I had missed before. What happened to the school teacher in the parallel world?

A lot is made in the movie of the fact that the military in our world believe that the Source Code is not a real world, it is just a replay of what already happened in our world. The soldier doesn't believe this, he is convinced that the Source Code is a real, parallel, world.

If the military are right then there's no problem. But if the soldier is right then what is happening to the school teacher every time the soldier takes over his body? Is his consciousness just vanishing?

At the end of the movie it does look like the soldier is right. His world carries on. So what has happened to the school teacher? Is he possessed by the soldier for the rest of his life? What about his friends and family that the soldier doesn't even know?

Suddenly I thought "Aha. Maybe his world didn't carry on. Maybe he did die when his life support was turned off and the end of the movie is his brain just running down... carrying on the fantasy as long as it could."

But there is a problem with this interpretation: the soldier sends his handler a message to prove that the parallel worlds are real and that he exists there as himself. Then again, he sends the message before he dies, so maybe the parallel worlds are real but only for that short time period. Either way, if the parallel worlds are real then the school teacher gets screwed somehow (pun intended).

After all this reflection I think it was a mistake to have the soldier sending the message to his handler. It would have been better to just leave the question open as to whether the worlds were real or not. As it stands, in trying to find a happy ending, we are left with the unpalatable suggestion that the poor school teacher just got wiped out of existence.