If Narcomoeba is revealed or looked at while moving from your library to your graveyard (such as with Mind Funeral), its ability will trigger when it's put into your graveyard. It was still in your library while it was revealed or being looked at.
If Narcomoeba is removed from your graveyard before its ability resolves, it won't be put onto the battlefield.
EDH / Commander: Restricted
Pauper: Ej legal
Premodern: Ej legal
93/94: Ej legal