diff --git a/dotCMS/src/main/java/com/dotcms/content/elasticsearch/business/ContentletIndexAPIImpl.java b/dotCMS/src/main/java/com/dotcms/content/elasticsearch/business/ContentletIndexAPIImpl.java
index cb675e4d76f..e4a562ac09d 100644
--- a/dotCMS/src/main/java/com/dotcms/content/elasticsearch/business/ContentletIndexAPIImpl.java
+++ b/dotCMS/src/main/java/com/dotcms/content/elasticsearch/business/ContentletIndexAPIImpl.java
@@ -3264,8 +3264,11 @@ private void mirrorDeactivateToOsStore(final String indexName) throws DotDataExc
      */
     @Override
     public long getIndexDocumentCount(final String indexName) {
-        return router.readProvider().getIndexDocumentCount(
-                indexAPI.getNameWithClusterIDPrefix(indexName));
+        // Resolve the physical name through the read provider's own toPhysicalName so the OS read
+        // path (phases 2/3) receives the .os-tagged name. getNameWithClusterIDPrefix adds only the
+        // cluster prefix (no .os tag), so under OS reads the index was reported as not found.
+        final ContentletIndexOperations readProvider = router.readProvider();
+        return readProvider.getIndexDocumentCount(readProvider.toPhysicalName(indexName));
     }
 
     /**