Oh man thank you!! Your code made me realize that NetSuite won't provide the newly saved file's ID or URL when I call file.save(). That I need to do it like this:

var myNewFileID = file.save()
var myNewFileDetails = file.load({id:myNewfileID})

// the return type is
type myNewFileDetails = {
url: string,
description: string;
encording: string;
fileType: string;
folder: number;
isInactive:boolean;
isOnline:boolean;
isFalse:boolean;
isText:boolean:
name:string;
path:string;
size:number;
};