What I would do is look at the Fall back status reports for Client Assignment failures. There you will have a count and maybe a reason why the client failed to become assigned clients.Kent Agerlund | My blogs: http://blog.coretech.dk/author/kea/ and http://scug.dk/ | Twitter @Agerlund | Linkedin: /kentagerlund

Is it possible to create a query in SCCM to display clients that has the Site Mode = Unknown?

Why would you like to query that? It is not a correct information. You can refer to the following thread to resolve the issue. Site Mode = Unknown after OSD http://social.technet.microsoft.com/Forums/en-US/configmgrosd/thread/d9adbe48-74fd-47d6-92bf-d26410367b63/Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

I too was looking for a query that would show me all computers that have a Site Mode of unknown. I did fix our issue and as of now all OSD going forward the site mode shows as Mixed like it should, but I have a handful of computers out there that still show unknow. It would be nice to run a query, then based on that uninstall and re-install the ccmsetup.exe.