News of Forest's bid for the England Under-19 international had barely broken before Everton fans made their feelings known, singing his name throughout Saturday's draw at Bournemouth and warning of a "riot" if the club pushed the sale through.
Chairman Dan Friedkin himself led the board's discussions, which ended with a unanimous decision to reject Nottingham Forest's offer - a package that included the sell-on clause typical of deals for the club's most promising academy graduates.
Armstrong, regarded as the finest talent to emerge from Finch Farm in years, played 87 minutes of the Bournemouth draw before being replaced by Charly Alcaraz, taking his tally to 24 appearances for the club.
Manager David Moyes, visibly caught between his players and the club's hierarchy, chose his words carefully afterwards.
"I think you always have to consider supporters; supporters aren't always wrong," he said. "But then there are also times where I've had people at clubs who are really powerful and make difficult decisions.
"Managers have to make decisions on players sometimes and they feel like huge decisions. But there are sometimes bigger decisions to be made and the club will, I'm sure, make what they think is the right one."
Asked what he would say to the fans, Moyes added simply: "Their manager's an Evertonian."
The episode represents an early test of trust between Everton's American owners and a fanbase already wary after years of instability under the previous regime. Selling a homegrown talent to a direct rival, in the closing days of the window and for a fee some considered light given Armstrong's potential, would have carried real reputational risk regardless of the financial logic behind it - a risk the Friedkin Group ultimately decided was not worth taking.
The affair comes at an awkward moment for a club still working to convince supporters that its new owners understand the weight of decisions like this one. Everton have leaned heavily on academy graduates in recent seasons as financial pressures limited transfer activity, and Armstrong in particular has been held up as proof the system still works - which made the prospect of cashing in on him, however lucrative, especially difficult for fans to stomach.