Well, you can call this an inside job if ever that has actually happened. But as what I mentioned above if you still care can you show us the BTC wallet address where do the funds stored since you said that you still have the access to your wallet. You can compare the "Total Received" of the wallet and the transaction made of the wallet if there is.
It wasn't inside job, it was a bug.
My wallet address is: 16io8zfbhStqe9WVdHN3JLzc29D73okaoy
You can see that most of the transactions there were made from blockchain.info IP address.
The thief address is: 1HKywxiL4JziqXrzLKhmB6a74ma6kxbSDj, and the transaction to it was not done from the same IP address (note that this is the same address as here:
https://www.coindesk.com/blockchain-info-issues-refunds-to-bitcoin-theft-victims/).