What's good about designing a site or an app before actually having it developed, and of course knowing the tech used for it (in this case, knowing how nostr works, but not necessarily knowing how to code), is you get a clear picture on how to actually develop it and consider multiple different scenarios of which a user may encounter during their use of the site or app.
With that said, if anyone's working on a store that sells digital (maybe physical too) products, if the author has requested the event deletion of the store page, where users have already purchased the product on that page and they'd like to revisit what they've purchased, it would be difficult for the user to even know what they've purchased and difficult for clients to showcase that / help them with it, so I'd imagine one has to put some information, that was previously within the product page, inside the purchase receipt event file and not just the product event ID, which would result in providing those who purchased the product to still have some information of what they've purchased and for clients to know how to deal with something that has been deleted, yet purchased.
This results in respecting the two sides of an intersection, where the original author would have (hopefully) the store page deleted and no new people seeing it, while those who purchased the product before then to still have some basic information about it without having that information exposed by default to the general public that hasn't purchased it.