Ella Birchenough, 16, tried to fish her two-week-old iPhone 5s from the drain using her feet after it slipped from her grasp in Eaves Road, Dover, Kent.
But she became stuck fast in front of a group of onlookers, including her mother, Joanne Birchenough, who rushed to the scene.
Firefighters eventually had to be called to ease Ella out of the tight spot - before she dashed home to have a bath.
Pictures of the GCSE pupil wedged in the drain went viral online. The teenager told ITV's Daybreak that she could not stop laughing.
She said: "I dropped it and I tried reaching for it and couldn't get it. I could reach the floor so when I got pulled out I went back in.
"Nobody said don't do it. They just looked at me as if I'm nuts. I just couldn't pull myself out in the end.
"I was just laughing and laughing."
Mobile phone shop employee Tim Richards, 22, was driving home with his mother when he saw Ella up to her waist in the drain, and they pulled over.
He told Daybreak: "She was in high spirits with a smile on her face, which you certainly don't expect to see on a girl stuck down a drain."
Yesterday Mrs Birchenough joked that she will be bringing out the pictures of Ella waist-deep in the drain on her 18th birthday and wedding day.
Taxi firm worker Mrs Birchenough, 36, said: "I think it's the funniest thing. At first I panicked, thinking 'Oh my God, she's going to sink'.
"But when I saw her it made me laugh. She is upset about her phone, but at the end of the day at least she's alright."
The schoolgirl's efforts eventually proved to be in vain - because the phone, which was on a contract, is broken.