Alpine only learned of Fernando Alonso's decision to join Aston Martin next year from the press release the British team sent out on Monday morning.
Alonso will replace the retiring Sebastian Vettel next year after signing a multi-year deal despite having an Alpine contract extension offer on the table.
In the build-up to the Hungarian Grand Prix Alonso downplayed suggestions he would switch teams, but the confirmation he had signed came the morning after the race, leaving Alpine blindsided.
"It was the first confirmation I had," Alpine boss Otmar Szafnaurer is quoted as saying about the press release by Motorsport.com.
"Obviously, when we're in the paddock, there's all sorts of rumours, and I had heard rumours that Aston were interested.
"Once you hear that they're interested, there's probably discussions that took place and there's some other indications that discussions took place, like walking out of the same motorhome at the same time, all that kind of stuff, which I saw.
"But I was confident that, even with the discussions, and there's nothing wrong with exploring, that we were very close.
"So yes, the first confirmation I had was the press release. I did ask the question [to Alonso]. And I was told: 'No, no, I haven't signed anything.' So I was a bit surprised."
Alonso is in the final year of his current Alpine deal but was discussing an extension. As recently as Thursday he told media he planned to stay at Alpine, but Szafnauer indicated the length of the contract on offer -- a single year plus an option for another year -- was the main sticking point.
Alpine felt confident Alonso was close to signing that deal. Szafnauer said his last conversation with Alonso in Budapest left him in no doubt that would be the outcome.
"There were just a couple of minor points that were outstanding, as he said that his lawyer would get back to us on," Szafnauer said. "I believed that to be the case.
"And then, before he left, I confirmed with him that we would be signing soon. And he said, 'Yeah, don't worry, I haven't signed with anybody else. We'll continue this in the next couple of days'"
Szafnauer added that he hasn't been able to get in touch with Alonso since the news broke, saying he's "on a boat, I think, in the Greek Isles somewhere."
Szafnauer said he also fielded multiple calls from other drivers about the vacant Alonso seat.
While Alpine junior Oscar Piastri seems like the obvious candidate to fill that seat, recent discussions between the Australian and McLaren appear to have muddied the waters about what his immediate future looks like.