Wiktionary
ships that pass in the night
n. 1 (context idiomatic English) Two or more people who encounter one another in a transitory, incidental manner and whose relationship is without lasting significance; two or more people who almost encounter one another, but do not do so. 2 (context idiomatic by extension English) Things which have no significant connection or commonality.
Usage examples of "ships that pass in the night".
They missed each other by about five yards, passed at full steam doing at least eight knots, like ships that pass in the night but speak not to each other in passing, and hurtled onwards to their doom.
Galaxy full of ships that pass in the night and every fool onboard thinks it's unique-I'm supposed to remember it half a lifetime later.