'unexpected appointment' is correct and can be used in written English.
It is often used to describe a situation in which a person unexpectedly must go to an appointment, either planned in advance or at short notice. For example: "I was running late but still managed to make it to my unexpected appointment on time."
But in 2005, Arrigo found herself with an unexpected appointment.
Andrew Bailey's year started with his unexpected appointment as chief executive of the Financial Conduct Authority.
It is little wonder that Michael Gove has kept an uncharacteristic low profile since his unexpected appointment last month as Justice Secretary.
Mr Pociatek, a restaurateur known more for his penchant for flashy motorcycles than for his familiarity with public finance, was a particularly unexpected appointment.
Four days after his unexpected appointment, Mikhail Y . Fradkovwas approved as prime minister by the Russian Parliament on Friday, following little debate and only a cursory discussion of his policy goals.
He was called a "young 70" by the New York Observer upon his unexpected appointment to the music directorship of the New York Philharmonic, in 2001; many of us had expected him to last professionally into his nineties, since his father, Lincoln Maazel, also a musician, passed away at the extraordinarily ripe age of a hundred and six.
In an unexpected double appointment, the council said that Winnacker will serve for just half of the expected 5-year term.
Because Fitz gave Jake an unexpected new appointment: He is now officially in charge of B-613, and Olivia's father is out.
The unexpected and bizarre appointment of Ruud Gullit as Terek manager and his subsequent sacking five months raised eyebrows.
However, some patients were also missed at both time points due to unexpected changes in appointments without communication to the investigators.
In his time at Shrewsbury, Turner had taken the club from the Third Division and turned them into to a solid Second Division outfit, but his appointment was unexpected.
