In the Odyssey, Hermes takes flight to Ogygia, Calypso's island, at Zeus's command to tell Calypso to let Odysseus go home. When he arrives Calypso recognizes him right away because:
the gods all know each other, no matter how far they live from one another
Retrieved, paragraph 7
How true is this? Is there a point in Greek mythology in which a god does not recognize another?