It is very doubtful that your local Building Department would have required plumbing schematics when your house was built. I have only ever heard of one Building Department ever requiring plumbing schematics.
Even if plumbing schematics are available, they do not show where the pipes are, just how they are laid out, and they wouldn't be "as-builts", only proposals.
The best way to find out is to find out where the building drain leaves the basement. This is found by the cleanout that you will find in newer homes. Not so much in older houses. It will be a 4 inch ABS screw cap that is left level with your concrete floor slab. If you know this location, it would be the shortest route to the plumbing fixtures. There is no science to it as many of the elbows will be 45 or 90 degree elbows and you never know where they will be.
Sorry for the bad news. Hopefully it is not an emergency.
Many years Building Inspection field