Which mailing list they were posted?
According to Aaron Van Wirdum in a 2018 article in Bitcoin Magazine the 1998 proposal was a private communication.
Szabo first came up with Bit Gold in 1998, though he only fully described it in public in 2005.
…
By 2008 — 10 years after first proposing it in private — Szabo brought up Bit Gold on his blog once again
(my emphasis)
This would explain why it is not in any public record from 1998. It wasn’t distributed to any public mailing list.
