Coinbase says that the wallet address is not linked to my coinbase account...however this is not true as transaction #1 for $600 roughly went into my coinbase wallet...transaction #2 is still sitting on the block chain and is roughly $4,000 which is a lot for me.
Does Coinbase show you a history of all deposits? I'm not familiar with Coinbase, but assuming it does, it will prove you've used that address before.
Can you post what exactly you sent to Coinbase? From what I've seen about support from exchanges, it helps to be very clear and only to the point, so they can forward it to someone who can actually fix this for you.