He had no last known location because he was not real. Even if he were, he was a god, and thus, omnipresent.
Page 309
Olympus
i think her last place was athens
the function of Poseidons temple was for Poseidons honor.
he was eaten by his father so there no way to know
mt. olypus
You do know that she's not real, right? She can't have a "last known location" if she never existed.
in a battel
Rhea.
cronus
I don't know for sure, but I think it's where her last "battle" was.
Neptune