Currently when a reward is a free product they are only able to copy the discount code and the link has to be the same for all free product rewards so it is not possible to link to the product. We use products that aren't public so they can't even search for them, even though that is still a pain to make them do. If giving a free product claiming that reward should add it to their cart, or at the very least apply the code and link them to the product page to add it.