You normally shouldn't expect to see all your devices listed here, unless they are child devices of the hub, or one of the 16 'best' neighbor routers that the hub is capable of tracking (or, if there has been a recent route request for a path to a non-child device, in which case it will appear in the Route Table Entry section (along with a 'via' first-hop destination router; but those entries age out if the route has gone unused for a certain amount of time).
If you haven't done so already, unplug/replug your mains powered repeaters (like the Garage Outlet device listed in the Neighbor table). See if anything in the table changes afterward.
Might be worth revisiting this thread (relating to spontaneous PAN ID change):
From @markus post in thread:
How to use this information to troubleshoot mass dropout of devices you may then ask? Look for a PAN ID change. Since the PAN ID will not update in the UI until after a reboot of the hub, if you have lots of Zigbee devices drop all at once, write down your current 16-bit (2 bytes, 4 characters) PAN ID (NOT the 64-bit EXTENDED PAN ID). Then reboot your hub and look for a change in the PAN ID, if it has changed you have your culprit for the drops. If this happens more than once, change your Zigbee channel (there are whole threads discussing which ones to use, you probably don't want to use the one I chose). When changing your Zigbee channel you probably will have to re pair many of your devices, but there is no need to delete them from HE, just pair them again.
