Disable textfield quantity in card

Are you sure that you didn't remove the delete icon as well when deleting the quantity field ?
Both are next each other so maybe you removed both ?

Indeed, if you hide the quantity field, the delete icon doesn't work.
Could you go in the menu Display->Views and edit the file cart of the view product and change the line:
<a href="<?php echo hikashop::completeLink('product&task=updatecart&cart_product_id='.$row->cart_product_id.'&quantity=0&return_url='.urlencode(base64_encode(urldecode($this->params->get('url'))))); ?>" onclick="var qty_field = document.getElementById('hikashop_cart_quantity_<?php echo $row->cart_product_id;?>'); qty_field.value=0; document.hikashop_cart_form.submit(); return false;" ><img src="<?php echo HIKASHOP_IMAGES . 'delete2.png';?>" border="0" alt="remove product" /></a>


to:
<a href="<?php echo hikashop::completeLink('product&task=updatecart&cart_product_id='.$row->cart_product_id.'&quantity=0&return_url='.urlencode(base64_encode(urldecode($this->params->get('url'))))); ?>" onclick="var qty_field = document.getElementById('hikashop_cart_quantity_<?php echo $row->cart_product_id;?>'); if(qty_field){qty_field.value=0; document.hikashop_cart_form.submit(); return false;}else{ return true;}" ><img src="<?php echo HIKASHOP_IMAGES . 'delete2.png';?>" border="0" alt="remove product" /></a>

That should solve the problem