Who do I contact in order to have the purchase order for something sent to me?

[Alwin Alcott 11,427]

you can go to your account, if it's MP you find your history there

also in your L$ account at your profile you find your payments.

[Alwin Alcott 11,427]

you can go to your account, if it's MP you find your history there

also in your L$ account at your profile you find your payments.

[Amethyst Jetaime 1,579]

Send the merchant a message about receiving a partial order.  Check their profile to see if they prefer and IM, notecard, or email.  Paste the transaction information in the message.  Then be patient as not all merchants are online every day. 

If you purchased in world, the transaction information is in your transaction history on your dashboard.  If you purchased on Marketplace, it is under My account in the marketplace.  Look for order history.