Hi,
If you don't want the URL to change, you can activate the "Use AJAX when possible for add to cart buttons" option of the configuration.
However, in some cases, like when you have custom item fields or options on your product pages, the AJAX mode won't be usable and thus the URL will still change.
Normally, the latest version of HikaShop should have some code to avoid the removal of an item from the cart to keep the popup parameter in the remove link and thus avoid the problem. So if you have an old version of HikaShop, I would recommend to update.