That means either you factory reset it before excluding it properly, or the device had some sort of malfunction and factory reset itself.
You should be able to pair it back. What hub do you have? I think the C8 may have issues onboarding those really old Leviton devices, but if they migrated from something like a C7 they would work.
As for the ghost node issue, here is the unofficial guide:
How To Remove Ghosts using hub tools or a UZB Stick
