Sharepoint - Cannot Create Managed Property for ows_UniqueId. It's not an option in the Mappings window.

Question

I'm trying to run a search query using Sharepoint search, and I'm trying to grab the GUID of the items within a list (be it in the Pages, Documents, or Custom List). Many posts talk about defining a managed property tieing it to ows_UniqueId. The problem I'm having is that I do not see ows_UniqueId as an option in the mapping list window.

Any ideas on where I can find this? Or is there a better option in acquiring the GUID of these items using Sharepoint Search?

Thanks in advance