It was in the sorting hat, where it was when Harry needed it to kill the basilisk. Only a true Gryffindor would find it there when needed.
Ok, I ran this crazy theory by a friend today. From the info in the book, it’s clear that Harry killed Voldy in 1997. Then the epilogue is 19 years later, 2016. My theory is that that’s when we can expect the next “Potter” book from J.K. Yeah, I know she’ll deny it. But numbers don’t lie. : )