If you want to store information for the next billions of years, carve it in a super-material and store it secretly in the Kaapval Craton, so that even when all current continents are gone and a new super continent is formed it has a high chance of survival (https://en.wikipedia.org/wiki/Kaapvaal_Craton)
Then again, if people did not find your message in all those billions of years it was so well hidden that they will probably not find it also in a couple of billions of years, but at least it remains