Well it doesn't make sense to me that Coinbase would take out all the contents of your account except for 0.00002 BTC. In my opinion it looks to me that you only have around 0.00002 BTC in the actual account, and you just inspected the element of the webpage to get it to look like 300~ BTC.
Inspect element can do what you are saying and it will be undetected even in forensic image report.
Please read the full thread op has said that he has two wallets/accounts each with around 300 btc.
Coinbase is a legitimate company but do you know some members in my company society had accounts in coinbase and they die in a machine fault in my mill so how will coinbase will take care of their funds...
I think they will eat them all...