Hello,
Check this Thread: https://www-secure.symantec.com/connect/forums/how-do-i-find-unmanaged-computers-also-deployment-doesnt-work
With SEP12, we decided to merge the old clientremote tool and Find Unmanaged Computers into one. The new version is called the Client Deployment Wizard.
You can find it in two places - first from the Home screen, choose "Install Protection Client to Computers" from the "Common Tasks" drop down at the top right, or alternatively, from the Clients tab, when you are in the client list, click "Add a Client" on the left hand side, just above "Add computer account"
Both will launch the CDW and allow you to search your network, find all your PC's and helps you deploy the right client to each one.
Idea has been raised for same to bring it back, you can vote for same
https://www-secure.symantec.com/connect/ideas/sepm12-bring-back-find-unmanaged-computers-sepm11
In your case, you could use the "UnManaged Detector" as an option.
Upon booting, a computer sends out Address Resolution Protocol (ARP) traffic to identify itself on a network. Once enabled, the Unmanaged Detector listens for gratuitous ARP traffic and collects Internet Protocol (IP) and Machine Address (MAC) data from traffic passing it on the local network. This data is then forwarded to the Unmanaged Detector’s SEPM which compares the IP address and MAC address of detected systems against its known list of managed endpoint clients and reports on the unmanaged endpoint clients.
An unmanaged detector is configured by right-clicking a managed SEP client in the Clients page of the SEPM console, and selecting "Make unmanaged detector".
Best Practices: When to use the "Find Unmanaged Computers" or "Unmanaged Detector" features in Symantec Endpoint Protection 11.0
http://www.symantec.com/docs/TECH104340
What does it mean to set a client as an Unmanaged Detector?
http://www.symantec.com/docs/TECH105722
Hope that helps!!