Depending on whether you're a Metallica fan or not, this is either good news or bad news.

Guitarist Kirk Hammett recently revealed on Jamey Jasta's podcast that he had lost his iPhone - along with 250 new riffs that he has been unable to recover.

Hammett had temporarily recorded the riffs onto his phone, but hadn't backed them up to iCloud. Tut tut, Kirk.

"I was crushed," he said. "It didn't get backed up. When it happened, I was bummed for about two or three days... I'm still looking for it to this day... It still might turn up, I'm hoping that it will. 

"I just chalked it down to, 'Maybe it just wasn't meant to be', and I'll just move forward with it... All you musicians out there who use your phone, make sure it's backed up, right?"

Metallica are currently working on the follow-up to 2008's 'Death Magnetic', which Hammett says is "25% done."