Not sure this helps, but if the address you used(12ngg3CB9VDvkbFDx7JKY92i9kYgDmiEaj) was a one-time address from coinbase. Then coinbase would have the would have the private key to address (12ngg3CB9VDvkbFDx7JKY92i9kYgDmiEaj), depending on their program, they should be able to sweep it again into your account.
This could be the issue...how do I know if it was a one time address...I do not believe I was scammed. I generated the 12ngg address sent the first transaction and without going back to coinbase to generate another wallet address for the same account I used the 12ngg...could this be the problem? The main concern is that coinbase keeps saying it isnt linked with them...when clearly the first transaction went through but was rerouted? to another address beginning 36ii5