It had appeared in the codex for Auridon antiquities. It was one of the few leads I found before I got Greymoor and had expired, sadly, as it is one of the antiquities that I really want! So there was only the icon for it, and moving the cursor over it, the message that I would need to find a new lead to scry for it.
But it is no longer listed there, or for any of the zones (I don’t know why I checked every listing but I did). I’ve been buying Auridon treaure maps and searching, searching, getting serpent shrines and motifs, but no Echoes of Aldmeris yet. I would think that’s just RNG, but not finding it in the codex any more made me worry that there is some bug, that it’s temporarily disappeared or something. I want to make sure it’s available and that I’m looking in the right place and can expect to eventually find it.