What do you mean your train was moved?

You are in a very expensive part of France! Try using Booking. Com or similar booking sites. Good luck

What train and route? There must  be other options to travel for you.

Most often for young people the cheapest will be the youth-hostel, auberge de jeunesse (in FR there are even more as 1 chain-but you need sometimes to be a member for it.

And you have a pass and thus can travel-that site of booking.com you can also set to many more searches, it will also show hostels, but in this very busy hi-season peak time the choice for still open will be limited.

If the train is cancelled or you have missed a connection SNCF the train company has to provide you a new reservation/train/bus/taxi to your destination or a hotel room. 

If you missed the train because you was to late in the station than it is your foult.