add: threads disappearance

docs/docs/guides/error-codes/missing-thread.mdx

@@ -0,0 +1,25 @@
+---
+title: Thread Disappearance
+slug: /troubleshooting/thread-disappearance
+description: Troubleshooting steps to resolve issues threads suddenly disappearance.
+keywords:
+  [
+    Jan AI,
+    Jan,
+    ChatGPT alternative,
+    local AI,
+    private AI,
+    conversational AI,
+    no-subscription fee,
+    large language model,
+    troubleshooting,
+  ]
+---
+
+When you encounter the error of old threads suddenly disappear. This can happen when a new, unintentional file is created in `/jan/threads`.
+
+It can be resolved through the following steps:
+
+1. Go to `/jan/threads`.
+
+2. The `/jan/threads` directory contains many folders named with the prefix `jan_` followed by an ID (e.g., `jan_123`). Look for any file not conforming to this naming pattern and remove it.