Hi,
I could not reproduce your problem.
Please be sure that your confirmed the user creation using the same browser than for the registration.
Your cart is in the session, linked to the browser. If you confirm the registration in another browser, the browser won't have the same session so it won't have the cart.
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.