Hi,
For HikaShop, the delete button is displayed by the file "show_products" of the view "order" with this code:
<a onclick="return window.orderMgr.delProduct(this, <?php echo $product->order_product_id; ?>);" href="<?php echo hikashop_completeLink('order&task=product_delete&order_id='.$this->order->order_id.'&order_product_id='.$product->order_product_id); ?>"><img src="<?php echo HIKASHOP_IMAGES; ?>delete.png" alt="<?php echo JText::_('HIKA_DELETE'); ?>"/></a>
But there is no view for after you click on the button. It just redisplays the view file.
So if you want to add processing when an order product is deleted, you want to create a small plugin of the group hikashop and implement the trigger onAfterOrderUpdate which will give you a variable $order with the products data allowing you to do what you need to do.