I am not sure I am following your question. If the device is not managed it should not have an inventory scan associated with it. Are you trying to wipe the device via exchange? What log are you seeing that error in?
The device is listed in the Mobile Inventory and upon right-clicking it, i get the option to 'EAS Wipe...' it.
Pg 12 of this document (http://help.landesk.com/Help/download/data/mobl/90/Mobility90Users.pdf) states that a LD agent is not needed for a wipe.
See screenshot of where i pulled the log: