Hello,
The "contact us" in the product page is handled by HikaMarket since it is possible to be sure who is the vendor of a product.
But the "contact us" in the order is not supported by HikaMarket, the main reason is that an order might not be handle by the vendor and that you can have multiple vendors in the same customer order.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.