When I merged the route and session so i could remove a hidden loco
the saved left trainz the started trainz again
everything but terrain and textures have disappeared
please help
Sounds like you merged the wrong way, it's merge Session to Route, not Route to session. Go into Edit Session and merge it to the route, that I think should should fix it.
Ok TS12\Userdata\Backups should be in one of the backup folders, if you haven't disabled them, the names may not be recognisable so look in each folder for a date before you merged it, then either import it using CM or just drag and drop into main window. Allow to overwrite.