sp_publication_validation procedure doesn't seem to work properly
My explanation is that sp_publication_validation validates a Publication: set of Articles sent by Publisher and received by Subscriber. Since there were no data corruption in transit this SP does not report any errors. 

To detect differences in replicated tables use SP_TABLE_VALIDATION.


  Either returns rowcount or checksum information on a table or indexed
  view, or compares the provided rowcount or checksum information with
  the specified table or indexed view. This stored procedure is executed
  at the Publisher on the publication database and at the Subscriber on
  the subscription database.


SP_TABLE_VALIDATION on MSDN