I have this mod installed but realized it no longer exists on the Nexus; any reason?

Edit:

Sea of Ghosts as well.

I have both of these quest mods installed and both are now missing from nexus.

In fact the author ThirteenOranges who created both these quest mods and a couple others no longer has any of them available outside of the steam workshop.

Maybe I'm wrong and he never featured these mods on the nexus?

You'll find those and Thirteenoranges other mods on Steam Workshop where they've received more updates from the author.

Edit: I believe he was banned on Nexus, I don't know why. But he has kept releasing mods on the workshop.