Exactly. Even though we have a many more means of storage today than we did in antiquity, they're brittle in innumerable ways. The only sort of "permanent" storage would be in the form of a hologram (if the media is durable), however without technology to read it, that's still a gamble.

This is why messages for nuclear waste disposal sites are meant to transcend not only modern media, but also modern language.

http://en.wikipedia.org/wiki/Waste_Isolation_Pilot_Plant#Mes...