The rockers are currently working on a follow-up to their hit 2008 record Death Magnetic, and Hammett admits he was devastated when he misplaced his cell phone and lost around 250 song concepts.

During an interview on The Jasta Show podcast, he says, "I put riffs on my iPhone, but something very unfortunate happened to me about six months ago. I lost my iPhone (containing) 250 musical ideas. And I was crushed. It didn't get backed up... I was bummed out for about two or three days... I just plain lost it. I can't find it. I'm still looking for it to this day. I just set it somewhere and... It still might turn up. I'm hoping it will. To try to remember those riffs...? I can only remember, like, eight of 'em. So I just chalked it down to maybe it just wasn't meant to be and I'll just move forward with it."

Hammett insists he will learn from his mistake and he urges other artists to back up their cell phone data, adding, "I make sure the phone is f**king backed up. All you musicians out there who use your phone, make sure it's backed up. Right?"