For people complaining in this thread, do you have any way to prove that you are without a doubt the account owner?
If you control the address that deposited the funds in the first place, you could send them a signed message.
Could also work with an old withdrawal address.
Then why aren't they asking for this instead of giving us impossible tasks? I have emails with withdrawal confirmations.. and yes my address is still the same unlike OP.
Edit: they unlocked it for me.