Your account at Coinbase has a deposit address. When you deposit coins to that address, Coinbase will move them to another address. You cannot use a block explorer (such as blockchain.info) to monitor your Coinbase account.
If your Coinbase account no longer has bitcoins in it, the account transaction history should tell you what happened to them.
This.
You can locate history through your account. If they aren't no where to see contact support as soon as possible but its likely to be that they moved them from your deposit address.
Thanks, I always wondered what them strange transactions were that I found in the block chain. And I have no transaction history on coinbase.