AC Milan looked short of match sharpness early on, with Strahinja Pavlovic gifting Celtic the opener through a misplaced pass that Cristian Duran punished in the 11th minute, before a mix-up between Samuele Ricci and Tommaso Liberali allowed James Forrest to double the hosts' lead just before the half-hour.
Camarda changed the complexion of the match after coming on at half-time, winning and converting a penalty moments after his introduction before adding a second with a header from a Samuel Chukwueze cross to complete the comeback.
Amorim, giving his first press conference since taking charge, put the shaky start down to his side still adjusting to a new way of playing.
"We tried to do the work we wanted, even if it wasn't easy. I had the feeling of watching a team that was trying to change its identity. Maybe we should have done better at certain moments, but that's normal when you're working this hard," he said.
Asked about the gulf between Milan's two halves, he added: "Sometimes it goes that way, we conceded a strange goal. Then in the second half we started better, we scored and when you do that sometimes you play differently."
On Camarda specifically, Amorim was unequivocal about his plans for the teenager: "He has to stay with us, I believe a lot in him and in our young players. I don't want to talk about individuals, but I can say Camarda will stay with us this season."
The head coach also touched on his side's overall approach, saying Milan had tried to dominate possession but "suffered a little" while attempting a high press that the squad has not yet fully absorbed, adding that more time was needed before the concept "gets inside the team."
He praised the effort shown in his first fortnight of training and gave a brief update on Mario Gila, whose Milan debut was cut short after half an hour with a thigh complaint: "He felt something, it shouldn't be anything serious, but we'll see."
The result came as Milan's transfer business continues in the background.
Youssouf Fofana's future looks increasingly likely to lie away from the club, with Saudi Pro League sides Al Nassr and Al-Ittihad both now credited with concrete interest in the France midfielder, according to Calciomercato.it, complicating what had appeared to be a straightforward move to Besiktas.
AC Milan are seeking at least €20 million for Fofana, who has made 88 appearances since joining from Monaco in 2024, scoring three goals and providing 13 assists, and are open to letting him leave this summer if their valuation is met.