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The most prominent iPhone prototype that Apple ever lost was the iPhone 4 that was forgotten in a bar by an Apple engineer months before its actual launch. But things could have been a lot different if a stranger had found a lost original iPhone prototype that was left in an airplane by Tony Fadell, who was in charge of iPod engineering at the time.

The best part of the story is that Fadell mounted up a massive search for the prototype, but the people searching for it didn't even know what they were looking for.

"Steve had expressly told me it was totally top secret. He said he was going to fire anyone who tells the world," Tony Fadell, who hasn't been working for Apple since 2010, told BBC in an interview. "I was sweating bullets," the former Apple exec said, as he was thinking about how he was going to explain to Steve Jobs that he lost an iPhone prototype.

Fadell got off a plane, and the iPhone was missing. "I was walking through every scenario thinking about what could happen," he said. "It fell out of my pocket, and it was lodged in between the seats!"

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According to Fadell, today does not mark the iPhone's 10th anniversary. It's the phone's 12-and-a-half year anniversary of the first iPhone, as development started years before Jobs actually took the stage to unveil it.

A few days ago, a prototype iPhone leak indicated that Apple toyed with the idea of having a click wheel iPod-like UI on the iPhone. Fadell somewhat confirmed that to the BBC, saying Apple was considering turning the iPod into an iPhone.

"We were turning it into a rotary phone from the sixties," Fadell said. "We were like, 'This doesn't work! It's too hard to use'."

The exec also recalled that elsewhere at Apple, a team of engineers started working on a touchscreen Macintosh computer. ""They had been working on this in secret. It was the size of a ping pong table. Steve showed it to me and said, 'I want to take that and put it on an iPod,'" Fadell said.

Fadell's full interview with the BBC is available at this link.