I have no idea because you didnt say if they are missing from the devices page on the hub or the z-wave details page or both? Not sure what you mean by "lost" exactly....
If they are missing from Z-wave details, a cloud restore with zwave radio would bring that back (but the device may not be paired anymore).
If they are only missing from the devices page a regular restore would bring that back.
If they are not missing from either then the devices are factory reset.
It actually sounds like the devices themselves got factory reset somehow. Maybe from a power surge? The only way to fix that would be to pair them to the hub again, I would suggest using the "Replace" method to get them back to the same node. This will prevent ghost nodes as well.
