Stolen Valor - evidences issue

Hi there, We completed the Stolen Valor mission twice in non-lethal mode. However, we can't find the last piece of evidence—it's always missing one each time. We've scoured the entire level 100 times. Nothing. Everything was packed up, everyone was secured. The weapon cache was closed, the weapon storage was reported. Everything. And yet we're still missing a piece of evidence... It's bugged. Has this happened to others?