If you check the original order confirmation mail from that site it has the following two clauses
and
So, if you've bought it directly from the rainforest site and you have been notified by email that it has been dispatched then your contract is complete and they can't change their minds.
For items purchased from third parties in Marketplace, this e-mail confirms the completion of your contract to purchase those items.
and
Please note that for items ordered from XXX this e-mail is only an acknowledgement of receipt of your order and your contract to purchase these items is not complete until we send you an e-mail notifying you that the items have been dispatched to you
So, if you've bought it directly from the rainforest site and you have been notified by email that it has been dispatched then your contract is complete and they can't change their minds.