Hi,
The "Joomla user id" is stored in the HikaShop user table ( user_cms_id ).
HikaMarket store the vendor administrator under the column "vendor_admin_id" ; the value is pointing to an HikaShop user id.
In the table HikaShop user ; you will also found a column "user_vendor_id" in order to link a user to a vendor.
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.