Only 105 days after the mutiny that forced him out, Mr Johnson was said to be taking soundings about entering the looming Conservative leadership race.
Mr Johnson made little secret of his resentment at being forced out and speculation was rife, even before Ms Truss's implosion, that he longed for a comeback.
“He's a winner and the only MP with legitimacy having been overwhelmingly elected by the country,” said one Johnson loyalist, Michael Fabricant.
“He may not be the first choice of MPs — I may be wrong — but he most certainly is amongst the membership.”
Another MP, Stephen McPartland, said his inbox was “inundated with local people saying we must bring back Boris”.
But other Tory MPs were far from enthusiastic. Sir Robert Syms said Mr Johnson was “not a serious candidate”, while Justin Tomlinson said a comeback was “wishful thinking”.
“I just think it’s too soon. I was there supporting him to the very end but he did lose the confidence of the majority of our colleagues,” Mr Tomlinson told Sky News.
Boris Johnson through the years — in pictures
Known for his colourful rhetoric and attention-grabbing antics, Mr Johnson led the Conservatives to a landslide general election victory in 2019.
But his premiership was dogged by scandals, most notably the Partygate affair, which saw him fined by police for breaking Covid-19 lockdown restrictions.
The relentless distractions wore down the patience of MPs, the public and ultimately his own ministers, who forced him out by resigning en masse in July.
He announced his resignation after conceding that he no longer had the confidence of the Tory benches.
However, he remained popular with much of the party grassroots and hinted at a comeback in his farewell speech in Downing Street, a mere six weeks ago.
Ms Truss succeeded him on a platform of cutting taxes and boosting economic growth, but her plans backfired when the financial markets went into near-meltdown. '
With the Tories now in dire straits in the polls, Mr Johnson is seen in some quarters as the party's only hope of winning the next election.
He has largely stayed out of the public eye since leaving office, except when paying tribute to the late Queen Elizabeth II.
A YouGov poll conducted this week showed that 32 per cent of Tory members would choose Mr Johnson to succeed Ms Truss.
Whether he can pull off a comeback is less clear. Many MPs are keen for a smooth succession to restore unity, and a Johnson return would be sure to produce division.
The rules for the leadership election have not yet been set, but rule-maker Sir Graham Brady may set a high threshold for MPs to enter the race.
Opposition MPs, who are calling for an early general election, were quick to say that Mr Johnson should not return.
Some Labour MPs pointed out that he still faces an investigation into whether he misled the House of Commons during the Partygate scandal.
“He shattered public trust in the government and plunged the UK into a political crisis. He must never be allowed near Downing Street again,” said Liberal Democrat MP Daisy Cooper.
Although comebacks by former prime ministers were once fairly common, only two have returned to Downing Street since the Second World War.
Wartime leader Winston Churchill returned for a second spell in 1951, while Labour's Harold Wilson served two separate terms in the 1960s and 1970s.