What he said. In less technical terms, when audio clips, information is permanently and irrevocably lost. You can pull the levels down, but you'd just end up with a white-hot mass of distortion at slightly reduced volume. There's no way to reconstruct whatever sound information was slamming into the microphone at the time that that recording was made.
It's always humiliating to go back to somebody and say something has to be redone because of a technical glitch, but in a lot of cases you can get away with being a bit vague about it. Not to the point of deceptiveness, but saying there was a "problem with the location sound recording" is more face-saving than disclosing that you made a dumb mistake which you've learned not to repeat. Or whatever the whole truth is.