New Brevoort Formspring

Hello Mr. Brevoort! While I haven't exactly kept up with the Asgardian side of Marvel's titles (I'm getting there. The new Thor series is off to a great start) I've noticed Thor has a metal arm covering that resembles Future Thor's from 'God of Thunder'. A comment on Comic Vine alluded to him losing it against Frost Giants. Honestly, I can't remember this happening or being mentioned. In what issue did this occur?