A simple Revit macro written in Ruby. Upon execution it detects and deletes all unnamed reference planes.

purge_unnamed_ref_planes.rb

load_assembly "RevitAPI"
load_assembly "RevitAPIUI"

include Autodesk::Revit::DB
include Autodesk::Revit::UI
include Autodesk::Revit::UI::Selection
include System::Collections::Generic
include System::Collections
include System

class ThisApplication < Autodesk::Revit::UI::Macros::ApplicationEntryPoint
  
  #region Revit Macros generated code
  protected
  def FinishInitialization
  	super
  	self.InternalStartup
  end

  def OnShutdown
  	self.InternalShutdown
  	super
  end

  def InternalStartup
  	self.Startup
  end

  def InternalShutdown
  	self.Shutdown
  end

  def Startup
  end

  def Shutdown
  end
  #endregion

  public
  def PurgeRefPlanes
    unless self.ActiveUIDocument.nil?
      doc = self.ActiveUIDocument.Document
      
      # collecting all ref planes in the project
      ref_plane_collector = FilteredElementCollector.new(doc)
      ref_plane_collector.OfClass(ReferencePlane.to_clr_type)
      ref_planes = ref_plane_collector.ToElements

      name_parameter_id = ElementId.new(BuiltInParameter.DATUM_TEXT)
      pvp = ParameterValueProvider.new(name_parameter_id)
      evaluator = FilterStringEquals.new()
      rule = FilterStringRule.new(pvp, evaluator, "", false)
      filter = ElementParameterFilter.new(rule)

      unnamed_ref_plane_collector = FilteredElementCollector.new(doc)
      unnamed_ref_plane_collector.OfClass(ReferencePlane.to_clr_type)
      unnamed_ref_plane_collector.WherePasses(filter)
      unnamed_ref_planes = unnamed_ref_plane_collector.ToElements

      transaction = Transaction.new(doc, "Purging unnamed reference planes")
      transaction.Start

      unnamed_ref_planes.map { |ref_plane| doc.Delete(ref_plane) }

      transaction.Commit
      TaskDialog.Show("Purge Unnamed Ref Planes", "#{ref_planes.Count} reference planes found.\n#{unnamed_ref_planes.Count} unnamed ref planes deleted.")
    end
  end

# Transaction mode
  def GetTransactionMode()
  	return Autodesk::Revit::Attributes::TransactionMode.Manual
  end

# Addin Id
  def GetAddInId()
  	return System::String.new("4596A3CA-FEB6-42C2-8EAA-81B0E9FE404D")
  end
end

This uses a simple selection method, simply searching for ref planes called "Reference Plane".
The next, proper version should check the built-in parameter Name which should be nil or empty for unnamed ref planes.

OK, done. Now it doesn't check the element name but instead the value of the parameter that populates the name.
Should work for all localizations.