At one point on Wednesday evening, more than 22,000 Britons were following the progress of a Nairobi-London flight online, waiting for now ex-International Development Minister Priti Patel to touch down.
When the plane landed, however, Mr Hariri was nowhere to be seen – and the consequences could have much graver fallout than Ms Patel’s tentative holiday meetings.
On Friday the President of Lebanon’s weak government, Michel Aoun, as well as Hezbollah Secretary General Hassan Nasrallah, both declared that they believed Mr Hariri had not returned to Beirut because he is being held in Saudi Arabia against his will.
The Prime Minister – who was appointed just over a year ago, ending a two-and-a-half-year deadlock in Lebanon’s parliament – amazed his aides and rivals alike with a surprise resignation delivered from the Saudi capital last Saturday.
Mr Hariri cited his inability to unite Lebanon’s disparate political parties due to foreign Iranian “meddling”, as well as his assassination fears, in a stumbled-over statement broadcast on Saudi television.
Later the same day he made a phone call to President Aoun tendering his resignation, which the President rejected. He has not been heard from since, Lebanese officials say.
Meetings and appointments in his calendar for this week were not cancelled in anticipation of any such move.
In a televised address on Friday, Hezbollah’s powerful Hassan Nasrallah threw Riyadh’s accusations of war-mongering in Yemen back at the Kingdom and claimed the Saudi authorities are holding Mr Hariri hostage.
“During the last year, Lebanon was in a period of political stability and the situation was good. A president was elected, a prime minister was appointed and a government was formed, Mr Nasrallah said.
“We condemn the blunt, bare-faced Saudi intervention in our domestic affairs.
“Any offence to the Lebanese prime minister is an offence to all Lebanese, even when he is our adversary,” he added.
Mr Hariri’s Sunni Future Movement party has long been backed by the Saudis as a bolster in Lebanon’s parliament against Shia, Iran-allied Hezbollah, but it is believed Riyadh had grown impatient with the Prime Minister’s inability to contain Hezbollah’s growing strength both at home and over the border, where it is fighting in Syria’s civil war.
Hariri’s own party has already called for his immediate return home for the “dignity of the nation”.
The international community remained remarkably quiet on the unprecedented Riyadh-Beirut tensions until Friday, when the US, French and German foreign ministries put out statements which said that they believed Mr Hariri was in Riyadh of his own free will.
A delegate travelling with French President Emmanuel Macron, who embarked on a surprise visit to Riyadh on Thursday, told the AP on condition of anonymity that Mr Hariri had told foreign ambassadors himself that he is not a prisoner in Saudi Arabia.
However, the French foreign ministry later offered more nuanced comments which suggested he may not be operating freely.
“We wish that Saad al-Hariri has all his freedom of movement and be fully able to play the essential role that is his in Lebanon,” deputy spokesperson Alexandre Georgini said in a statement.
The Lebanese premier is not the only person who is rumoured to be under house arrest after a week of frantic activity in Riyadh.
Crown Prince Mohammed bin Salman ordered the arrests of more than 200 people, including 11 princes, ministers and influential businessmen, in an anti-corruption purge widely viewed as a concentrated effort to consolidate his own powers.
US Secretary of State Rex Tillerson said from a tour of China that there was no reason to believe Mr Hariri was being prevented from returning to Lebanon but he is “monitoring” the situation.
The US supports “the legitimate government of Lebanon” and is “asking other outside parties to stay out of it,” Mr Tillerson added.
In Lebanon, however, the mood remains tense. Dozens of Saudi nationals left the country on Friday after an order from Riyadh for all citizens to evacuate – a decree issued four times over the last five years.
Many Lebanese are despairing over the collapse of a government which held so much promise a year ago, as well as the looming spectre of conflict if Riyadh has indeed decided the tiny country is the new front in its struggles against Iran.