I understand his situation there should be something or a guideline that a user needs to pass through so he can retrieve his account, it is his mistake but it could happen to anybody like newbies in the cybersecurity, support should address this issue as a show of concern to it's traders
Loosing the F2A is a MEGA disaster, almost like the guy who lost 104 Million in bitcoin, because he threw away his hard drive by accident.
How can you prove to a company residing in China that you are the lawful owner of the account? I don't see an easy solution to your problem.
Maybe writing a registered letter to the head of customer care? But the amount of time it takes to get this issue resolved should be the least of your worries, as - and I feel your pain - it could very well be that your coins are gone forever.