LIKE clause not working in hook query alter
Have you tried changing the hook you are using to MYMODULE_query_alter?

You are implementing hook_query_TAG_alter(), and I don't see where the Search query is tagged as such.

Per the Node API:


  This is the hook_query_alter() for queries tagged with 'node_access'.
  It adds node access checks for the user account given by the 'account'
  meta-data (or global $user if not provided), for an operation given by
  the 'op' meta-data (or 'view' if not provided; other possible values
  are 'update' and 'delete')