Although it is months later, I have just begun seeing this on a client’s site too. I maintain their site weekly and it has just happened in the last few days. Top menu gone, no signs of hack, nothing apparent in the dashboard to correct it. All menus look good in the dashboard.
Did you get your issue resolved? It is also interesting that the links to the go Theme Team support forum on ThemeForest are dead and even the image that is supposed to accompany that link is also dead. Only a missing image placeholder icon is shown. Does ThemeTeam have something embedded in their code that requires it to phone home in order to work?