diff --git a/sherlock_project/sherlock.py b/sherlock_project/sherlock.py
index e037d39458..a42722ccc2 100644
--- a/sherlock_project/sherlock.py
+++ b/sherlock_project/sherlock.py
@@ -170,6 +170,22 @@ def multiple_usernames(username):
     return allUsernames
 
 
+def check_message_query_status(response_text, errors, status_code) -> QueryStatus:
+    """Determine the query status for a "message"-type site.
+
+    The absence of the "not found" message is only meaningful when the server
+    actually answered the request. On a server error (HTTP 5xx) the body cannot
+    be trusted, so the status is UNKNOWN rather than a false CLAIMED.
+    """
+    if isinstance(errors, str):
+        errors = [errors]
+    if any(error in response_text for error in errors):
+        return QueryStatus.AVAILABLE
+    if status_code >= 500:
+        return QueryStatus.UNKNOWN
+    return QueryStatus.CLAIMED
+
+
 def sherlock(
     username: str,
     site_data: dict[str, dict[str, str]],
@@ -404,30 +420,9 @@ def sherlock(
                 query_status = QueryStatus.UNKNOWN
             else:
                 if "message" in error_type:
-                    # error_flag True denotes no error found in the HTML
-                    # error_flag False denotes error found in the HTML
-                    error_flag = True
-                    errors = net_info.get("errorMsg")
-                    # errors will hold the error message
-                    # it can be string or list
-                    # by isinstance method we can detect that
-                    # and handle the case for strings as normal procedure
-                    # and if its list we can iterate the errors
-                    if isinstance(errors, str):
-                        # Checks if the error message is in the HTML
-                        # if error is present we will set flag to False
-                        if errors in r.text:
-                            error_flag = False
-                    else:
-                        # If it's list, it will iterate all the error message
-                        for error in errors:
-                            if error in r.text:
-                                error_flag = False
-                                break
-                    if error_flag:
-                        query_status = QueryStatus.CLAIMED
-                    else:
-                        query_status = QueryStatus.AVAILABLE
+                    query_status = check_message_query_status(
+                        r.text, net_info.get("errorMsg"), r.status_code
+                    )
 
                 if "status_code" in error_type and query_status is not QueryStatus.AVAILABLE:
                     error_codes = net_info.get("errorCode")
diff --git a/tests/test_message_query_status.py b/tests/test_message_query_status.py
new file mode 100644
index 0000000000..dba250ab55
--- /dev/null
+++ b/tests/test_message_query_status.py
@@ -0,0 +1,34 @@
+"""Offline unit tests for message-type query status detection."""
+
+from sherlock_project.result import QueryStatus
+from sherlock_project.sherlock import check_message_query_status
+
+
+def test_available_when_not_found_message_present():
+    assert (
+        check_message_query_status('{"valid":true}', '"valid":true', 200)
+        == QueryStatus.AVAILABLE
+    )
+
+
+def test_claimed_when_message_absent_and_response_ok():
+    assert (
+        check_message_query_status('{"status":"success"}', '"valid":true', 200)
+        == QueryStatus.CLAIMED
+    )
+
+
+def test_unknown_on_server_error_instead_of_false_claimed():
+    # 502 body lacks the "not found" message; must not be reported as Claimed.
+    # Regression for https://github.com/sherlock-project/sherlock/issues/2950
+    assert (
+        check_message_query_status("Bad Gateway", '"valid":true', 502)
+        == QueryStatus.UNKNOWN
+    )
+
+
+def test_supports_list_of_error_messages():
+    assert (
+        check_message_query_status("user not found", ["no such user", "not found"], 200)
+        == QueryStatus.AVAILABLE
+    )