When you login hikashop checks whether or not you have a cart in your anonymous session. If yes, it links it to your user account. If not, it uses the last cart you had while logged in.
When you logout, the new anonymous session does not keep the cart.
That behavior should be consistent unless you have the problem on that thread:
www.hikashop.com/en/support/forum/4-how-...ml?limit=20&start=20
(there is also the solution there)
In that case, the behavior might be different based on whether you login from within hikashop or from joomla.