The zwave specification allows for what is called “whisper distance” for the initial exchange of the encryption key with a security device. It’s up to each manufacturer to implement this for their specific devices, but I think for almost all of them 5 feet would be treated very differently than 2 feet. That’s an intentional security measure.
A number of people have reported That the Schlage locks treat whisper distance a little bit differently than Yale and Kwikset.
If you attempt to pair a Yale lock outside of its whisper distance, The join will fail all together and you won’t see the lock on your network.
If you attempt to pair a Schlage lock outside of its whisper distance, The secure join will fail but sometimes the lock will go ahead and pair insecurely which leads to the really frustrating situation where it shows up as a device on your network but it won’t respond to any of the commands because it doesn’t have the encryption key. So you have to exclude it and try again.
With any zwave lock there can be yet a different problem which is that the secure join goes fine but there is no beaming repeater close enough to the lock to get the commands through when the lock is sleeping. But that’s an entirely separate issue.
Most Schlage lock problems at the time of initial pairing appear to be due to the whisper distance fail where the lock joins insecurely but then doesn’t have the encryption key. That’s why people say these locks are fussy about pairing. And why it’s almost always worth trying to get within 2 feet of the lock to do the pairing.
I agree absolutely that a device should not disappear after it has been successfully paired. I can imagine a situation where that might happen under the SmartThings architecture because of the fact that there are dual copies of the device lists, one in the cloud and one on the hub. But just because it might happen doesn’t mean it should. FWIW.