If it's the UK then it will be DHL. But yes, there isn't much you can do, the analogy I use is that your item is now in the post, and there is not much you can do to contact the mail processing office and ask them to fish out just your letter, it gets bulk processed along with everything else there. If you have urgent need of the item, well you will have to buy a replacement and charge it to BA. Otherwise the advice you were given is 100% correct - just wait until the courier can deliver it.