Thanks for your information. I realise the transfer of ownership takes place eg it in custody at the exchange - what I dont understand is that - as I thought it worked - all transactions are recorded in the blockchain and verified a nuber of times from independent copies of the blockchain - so how can a "person" claim ownership over this amount of coins and they dissappear?
I would expect a traceback option in the blockchain would be possible
If you can hide your traces of transaction or change of ownership then whats the blockchain fore?
Or is this a flaw in BTC code?