How to get the category/sub-category name in invoice/order

My opencart website has product that belong to many (almost all of the categories) that i have created. I am looking for a way to figure out from what category has the product been ordered from. I think that getting the category or sub-category name or id in the order should do the trick but in the products tab in the invoice, all I get is the product name, model no. and quantity. How can I get the category id as well?

Did you find an answer to this question?
Can you tell me as well if it's not much trouble?

Thanks.