No device got created on the hub devices, or you possibly deleted it on accident. Not very common for this to happen unless the device fails to pair. The system logs would have possibly shown errors during pairing if there were any. Possibly having the name blank in SS is what caused the issue?
Click the Discover button on the zwave details, with any luck it will be able to create the device. You might need to manually wake the device up before you click discover since it is a battery device.
Other option would be to exclude it and pair again, and hope it completes it all the way. Make sure you set a name in the SS list first. Then when you exclude it, it should pair back up almost immediately.