Hi Kevin,
First question are you're sure this Zwave 5 device is a non existing device.
If so did you by any chance reset 1 of the other 2 door sensers without removing it for the ZWave receiver ?
Now to your questions.
The zwave icon with a 1 means Status.Level 1
The undiscover ... if you do a discover on the zwave network, is zwave device 5 found ?
If so the only way i found to remove a phantom zwave device is a full reset.
And before doing so remove all other zwave devices !!!
And after the reset add all device again ... then your phantom device should be gone.
I hope someone has a better suggestion, but this is how i solved it
Cheers
Louis