Missing node_reference warning User warning: The following module is missing from the file system:
  node_reference. For information about how
  to fix this, see the
  documentation page. in trigger_error() (line 1138 of
  /[localdevetc/drupalrootetc]/docroot/includes/bootstrap.inc). =>


This error usually occurs when module files are removed without a module being disabled and uninstalled first. Typically it's corrected by simply re-downloading the module files and then uninstalling it. The problem is that there doesn't seem to be a module called node_reference for Drupal 7. I tried drush dl node_reference and got:


  No release history was found for the requested project
  (node_reference).
  Could not download requested project(s).


Any ideas?
node_reference is just a sub-module of the References module; that's why you can't download it using Drush. Instead, download the References module.

drush dl references