Another example of real-world quirkiness. The village of Egginton has a bus stop which has just been refurbished, yet it hasn’t had a bus service since 2017. New bus stop installed in village with no bus services - BBC News
I couldn’t see a bus stop in OSM though.
disused:highway=bus_stop ?
Here in Lancashire bus stops occur and are occasionally used by buses as part of their route. Some bus-stops have not had a bus use it for years and then magically a bus starts using it. Wasn’t disused, just not used - it was always there.
Aha! A bus stop is still a bus stop even if no bus stops because there is potential that a bus stops not stopping and that bus stops at the bus stop 
I dunno if it even needs to be tagged as ‘disused’, it just won’t be tagged with any bus route relations 