Now that you've got your layout back, back it up! It's possible for a Trainz crash to actually corrupt the file you're working on past recoverability, especially if it occurs while you're editing the route in surveyor. (it doesn't happen very often, but it happens.) There are a lot of different strategies for this, but resaving every 1/2 hour or so with a new name (NorthWest001, NorthWest002, etc.) is one that works for me. That way no matter what happens I can at least revert to the previously worked on version.
Of course, if your hard drive goes south so will everything else. You might want to back up to an attached USB hard drive or other storage to be on the safe side.
--Lamont