Go to http://aem-host:porl/crx/de/index.jsp and log in as admin.

Go to Tools > Query

In the bottom Query box, enter the following query:
/jcr: root//element(*, cq: ClientlibraryFolder)

Validate whether your missing client library is in the results. If it appears there, then contact AEM Customer Care to get help with further investigation. Else continue to the next step.

If you find that the results excluded the missing client library, then go to http://aem-host:port/libs/granite/operalions/content/diagnosis/tool.html/granite:queryperformance.

Enter the query again and click Explain.

The output shows you which index is used to execute the query. If the index listed is not the nodetype index, then something is wrong.

You can debug what is causing a different index to return a lower-cost estimation for the query. Refer to this article for how to enable debug logging for query analysis.

If the correct index is picked but fails to return the correct result, then it is corrupted. In this case, you can reindex the nodetype index.

To reindex the index asynchronously, follow the steps in this article.