I agree with you that Coinbase Has the BTC and owes me. With that said, below is my message to Coinbase with tx history.
"Thanks you for your email. The Coinbase support link do not help with my unique situation. I've provided all the information that I have a my disposal. My recommendation is for you to follow the transaction. In short, I sent two bitcoin to an address from Coinbase on Nov 2016. The person returned the two bitcoin to me on Nov 2017 using the same sent address (aka hot address) from Coinbase. I have yet to resolve this issue. The links below are the two transactions for your reference".
https://www.coinbase.com/accounts/f1e08e66-6f38-5719-8939-452950f1029d/transactions/ab836c3c-c6af-5179-8bf6-75fe8c6eac70https://blockchain.info/tx/db3d3d44226fb444ee6bb9a66cbd0a46e84cd5b5962bde78a97ba88cc46aee48The person used the same address that I sent from (hot address).
1A8GjjLjypGRhZANRgEL6FiYZTqA4hrvDh
Thank for your help.