When a tracking device is removed from the field, you must also delete the device from the RSA Surveillance plugin.
What you should know
A tracking system does not inform the plugin when a device is removed from the system. When the plugin connects to a tracking system, it checks for new devices in the system and adds them, but it does not check for missing devices. If a device was removed from your tracking system, you must remove the tracking system from Security Center, and then add it back again.