If this was indeed some sort of hoax for publicity, it was a terrible idea, and he has destroyed his career, and he should face charges for the false report. If he was indeed attacked, it is horrible that it happened, and those responsible need to be punished to the full extent of the law.
However, the investigation is not fully complete yet, so it is premature to assume one way or the other. Right now, we need to wait and see.
As far as his phone, even if he was talking to someone at the time, why would they actually physically need his phone? I wouldn't want to turn my phone over to anyone, either. They generally auto lock, and you'd also have to give your unlock code, and there is a LOT of personal info on modern phones. An alternative, if they want to prove he was on it, would be to take screen shot of his recent calls OR go to the provider website and print out a list of calls and texts.