Bitcoins never showed up in wallet. Yet sender says transfer complete I've used a site called bit trade australia to buy and send bitcoins to a wallet on blockchain.info. Successfully three times this month, trusted too. 

Yet this time (after receiving an email from BTA, "your coins have been transferred" like normal) there is zero proof on blockchain.info of this happening. My wallet hasn't changed. No bitcoins. It's been 13 hours since that email. And I assure you, this has never happend to me before. 

Any ideas? Thank you, Regards.
This should be easy to prove or disprove using any block chain explorer.  Ask the sender to send you the transaction hash for the transaction where the coins were supposedly sent to you.  Then, do a search for this transaction hash using any block chain explorer (such as blockchain.info).  If a transaction is found for the hash, with your bitcoin address and the amount that you expected as one of the outputs, then this confirms that the sender did indeed make the payment to you.  Otherwise, the sender can't support their claim.