Restoring a single app's data from iCloud

You cannot. Restoring is all or nothing.

But what if you care so much about the data on that one app that you’re willing to do a complete restore? Can you please advise how to do that? My issue is similar, but I didn’t delete the app. The data is just gone. (Just to get ahead of things, I’d appreciate no impolite comments, please—This data relates to a loved one who has passed.) Thank you respectfully in advance.