“I literally turned on Sky Sports and I saw this yellow headline,” he said.
“My phone started jumping. I’m thinking, what’s this? ‘Mark Warburton resigns as Rangers manager’.
“I phoned [Rangers assistant manager at the time] Davie Weir, ‘Davie, I think I’ve just been sacked. He said, ‘so have I’ and I said, ‘why is that?’
“And I looked at the television again and it said: ‘David Weir also resigns’. Then I get a text saying ‘please look at your email account, we accept your resignation’. I have no idea what you’re talking about. And that was it.”
The BBC learned in 2017 that Warburton had been in contact with Nottingham Forest and was high on the English Championship club’s list of possible managers.
However, he was not offered the job and they decided to retain their interim team of Gary Brazil and Jack Lester until the end of the season.
Warburton, who managed Rangers for two years from 2015, is now in charge of Queens Park Rangers in the English Championship.
He says he receives two or three messages a week describing him as a “snake” for “walking out on Rangers”.
“No-one would walk out on Rangers,” Warburton said. “Who in their right mind would walk out on one of the big two [in Glasgow]?
“Especially, when you’re sitting in second [in the Premiership] ahead of a cup match… but that’s how we found out. We found out that we’d resigned. To this day it eats away.
“I’m very fortunate that I have a good job and there’s not a lot of jobs in football; we’re very privileged to manage clubs like Nottingham Forest and Brentford beforehand and now to be at QPR for three years. I’m now the third-longest-serving manager in the [English Championship], bizarrely.
“But that [Rangers exit] eats away at you because it’s such a privileged position to be manager of a club of that stature. And I felt, not in an arrogant way, that we were doing an OK job, the squad was young.
“The only way we were going to close that gap [on Celtic] was through money and we never had the money.”
At the time of Warburton’s departure, Rangers said in a statement: “At a meeting with the management team’s representative earlier this week, the club were advised that Mr Warburton, Mr Weir and Mr McParland wished to resign their positions and leave the club on condition that Rangers agreed to waive its rights to substantial compensation.
“Rangers’ agreement to waive compensation would assist the management team to join another club.”
The Ibrox club claimed Warburton’s representative attempted to alter the terms, adding: “A further board meeting was held… to discuss this and it was decided not to agree to this additional request but to hold with the original agreement.”
Warburton said his phone was “bombarded” following news of his departure, and that he couldn’t speak to his wife during the seven-and-a-half-hour journey from Glasgow to his family in England because of the volume of calls he was receiving.
“I found out that 249 texts is the most you can get before you have to restart the thing,” he added. “By the time I had deleted them they’d filled up again.”