diff --git a/swh/loader/core/loader.py b/swh/loader/core/loader.py
--- a/swh/loader/core/loader.py
+++ b/swh/loader/core/loader.py
@@ -11,6 +11,7 @@
 from typing import Any, Dict, Iterable, Optional
 
 from swh.core.config import load_from_envvar
+from swh.loader.exception import NotFound
 from swh.model.model import (
     BaseContent,
     Content,
@@ -331,6 +332,21 @@
             )
             self.storage.origin_visit_status_add([visit_status])
             self.post_load()
+        except NotFound:
+            self.log.exception(
+                "Loading failure, updating to `not_found` status",
+                extra={"swh_task_args": args, "swh_task_kwargs": kwargs,},
+            )
+            visit_status = OriginVisitStatus(
+                origin=self.origin.url,
+                visit=self.visit.visit,
+                type=self.visit_type,
+                date=now(),
+                status="not_found",
+                snapshot=None,
+            )
+            self.storage.origin_visit_status_add([visit_status])
+            self.post_load(success=False)
         except Exception:
             status = "partial" if self.loaded_snapshot_id else "failed"
             self.log.exception(
diff --git a/swh/loader/core/tests/test_loader.py b/swh/loader/core/tests/test_loader.py
--- a/swh/loader/core/tests/test_loader.py
+++ b/swh/loader/core/tests/test_loader.py
@@ -8,6 +8,7 @@
 import logging
 
 from swh.loader.core.loader import DEFAULT_CONFIG, BaseLoader, DVCSLoader
+from swh.loader.exception import NotFound
 from swh.loader.tests import assert_last_visit_matches
 from swh.model.hashutil import hash_to_bytes
 from swh.model.model import Origin, OriginVisit, Snapshot
@@ -135,6 +136,7 @@
 def _check_load_failure(caplog, loader, exc_class, exc_text, status="partial"):
     """Check whether a failed load properly logged its exception, and that the
     snapshot didn't get referenced in storage"""
+    assert isinstance(loader, DVCSLoader)  # was implicit so far
     for record in caplog.records:
         if record.levelname != "ERROR":
             continue
@@ -213,3 +215,26 @@
     _check_load_failure(
         caplog, loader, RuntimeError, "Failed to add snapshot!", status="failed"
     )
+
+
+class DummyDVCSLoaderNotFound(DummyDVCSLoader, BaseLoader):
+    """A loader which raises a not_found exception during the prepare method call
+
+    """
+
+    def prepare(*args, **kwargs):
+        raise NotFound("Unknown origin!")
+
+    def load_status(self):
+        return {
+            "status": "failed",
+        }
+
+
+def test_loader_not_found(swh_config, caplog):
+    loader = DummyDVCSLoaderNotFound()
+    result = loader.load()
+
+    assert result == {"status": "failed"}
+
+    _check_load_failure(caplog, loader, NotFound, "Unknown origin!", status="not_found")