The actress threw her husband’s iPhone in rage after a fight on her 30th birthday — then begged their LA building’s staff to help as she tried to trace it on an app on another phone, London’s High Court heard.

“When I entered the residence, Amber explained to me that she had thrown Johnny’s cell phone — and the wallet containing it — off the balcony the night before,” the building’s security guard, Starling Jenkins, said in a witness statement.

“The ‘Find My iPhone’ application indicated that Johnny’s phone was somewhere on the streets below the balcony of the residence,” he said.

Not seeing it during his initial search, Jenkins said, he “asked several homeless people if they had it.”

“One homeless man admitted to me that he had the phone,” he said, and was willing to give it back — for an unexpected price.

“He returned the phone to me in exchange for the following: (1) US$425; (2) three chicken tacos; (3) two bags of chips; (4) two apples; and (5) four bottles of water,” Jenkins said in his statement.

The phone was flung after a party that both Heard and Depp admit ended in violence — just disagreeing over who was responsible.

Heard has claimed her husband threw a bottle of champagne at her, grabbed her by the hair and threw her to the floor, which he denies. Depp claimed from the witness stand earlier in the trial that his wife threw a “haymaker” punch at him, then she or one of her friends left feces in their bed — which finally made him dump her, all of which she also denies.

Jenkins said that when he arrived at the building the day after the fight, Depp was long gone — and he “saw no marks or bruises of any kind on [Heard’s] face or body.”

He drove the “Justice League” actress to Coachella the next day with her sister, four friends and her dogs, he said in his statement.

“I heard Amber frequently express her anger [at] Johnny … but she did not say one thing or make any innuendos about allegations of domestic violence,” he told the court.

“She was hooping it up all weekend, and it was clear that she and her girlfriends spent much of the time at Coachella intoxicated.”

She “threw up at least once” in a car park and was “clearly dehydrated,” adding that he “had to obtain ginger ale and crackers for her.”

With Post wires