An example an empty search result with a warning

{
  "resourceType" : "Bundle",
  "id" : "bundle-search-warning",
  "meta" : {
    "lastUpdated" : "2017-03-14T08:23:30+11:00"
  },
  "type" : "searchset",
  "total" : 0,
  "link" : [{
    "relation" : "self",
    "url" : "https://example.org/fhir/Observation?patient.identifier=http://example.com/fhir/identifier/mrn|123456"
  }],
  "entry" : [{
    "fullUrl" : "urn:uuid:2866af9c-137d-4458-a8a9-eeeec0ce5583",
    "resource" : {
      "resourceType" : "OperationOutcome",
      "id" : "warning",
      "text" : {
        "status" : "generated",
        "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\">There is no matching patient for MRN 123456</div>"
      },
      "issue" : [{
        "severity" : "warning",
        "code" : "not-found",
        "details" : {
          "text" : "There is no matching patient for MRN 123456"
        }
      }]
    },
    "search" : {
      "mode" : "outcome"
    }
  }]
}