I placed an order for two pieces, but only one was shipped. The recipient let me know about that. Please ship the rest of one piece right away. And please make sure to let me know the tracking number when you ship it.
I've ordered two but only one is shipped. The recipient contacted me. Please send the other that is missing right away, and when you ship please do not forget the tracking number.
I ordered two of them but only one was sent. There was a message from the recipient. Please send the missing one as soon as possible. In that case, please send me the tracking number.