diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7d978995..319b8b18 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to
 - ✨(backend) add Traefik support via configurable media-auth url header #1649
 - ✨(backend) update a room's attributes from the external API
 - 🔊(backend) log request duration in Gunicorn workers
+- 📈(frontend) track missing lobby participant on accept/reject
 
 ### Changed
 
diff --git a/src/frontend/src/features/participants/api/enterRoom.ts b/src/frontend/src/features/participants/api/enterRoom.ts
index 2c8c618a..80d70d3a 100644
--- a/src/frontend/src/features/participants/api/enterRoom.ts
+++ b/src/frontend/src/features/participants/api/enterRoom.ts
@@ -1,5 +1,6 @@
 import { ApiError } from '@/api/ApiError'
 import { fetchApi } from '@/api/fetchApi'
+import { captureEvent } from '@/features/analytics/telemetry'
 import { useMutation, type UseMutationOptions } from '@tanstack/react-query'
 
 export interface EnterRoomParams {
@@ -17,13 +18,23 @@ export const enterRoom = async ({
   allowEntry,
   participantId,
 }: EnterRoomParams): Promise<EnterRoomResponse> => {
-  return await fetchApi<EnterRoomResponse>(`/rooms/${roomId}/enter/`, {
-    method: 'POST',
-    body: JSON.stringify({
-      participant_id: participantId,
-      allow_entry: allowEntry,
-    }),
-  })
+  try {
+    return await fetchApi<EnterRoomResponse>(`/rooms/${roomId}/enter/`, {
+      method: 'POST',
+      body: JSON.stringify({
+        participant_id: participantId,
+        allow_entry: allowEntry,
+      }),
+    })
+  } catch (error) {
+    if (error instanceof ApiError && error.statusCode === 404) {
+      captureEvent('lobby_entry_participant_gone', {
+        room_id: roomId,
+        allow_entry: allowEntry,
+      })
+    }
+    throw error
+  }
 }
 
 export function useEnterRoom(