diff --git a/public/js/ar/detect.js b/public/js/ar/detect.js
index 27998d6..3ab7bd5 100644
--- a/public/js/ar/detect.js
+++ b/public/js/ar/detect.js
@@ -5,10 +5,19 @@ export function createDetector() {
   return new AR.Detector({ dictionaryName: 'ARUCO_4X4_1000', maxHammingDistance: 0 });
 }
 
+/* Returns the markers usable for solving: present in the scene, sane geometry.
+ * The returned array also carries diagnostics so the HUD can distinguish
+ * "nothing detected" from "detected but not in the scene" — the latter looks
+ * identical on screen but means the scene never loaded, or the crest belongs to
+ * a different layout. knownIds may be null/empty; then nothing is solvable and
+ * rawIds tells you what the camera actually saw.
+ */
 export function detectMarkers(detector, imageData, knownIds) {
-  const markers = detector.detect(imageData);
-  // keep only markers that exist in the scene, with sane geometry
-  return markers.filter(m => knownIds.has(m.id) && quadArea(m.corners) > 100);
+  const raw = detector.detect(imageData).filter(m => quadArea(m.corners) > 100);
+  const usable = (knownIds && knownIds.size) ? raw.filter(m => knownIds.has(m.id)) : [];
+  usable.rawCount = raw.length;
+  usable.rawIds = raw.map(m => m.id);
+  return usable;
 }
 
 export function quadArea(c) {