As of today, any PA app is visible to users, only if its shared or given access (Edit/View). Now somehow, if a user who doesn’t have access receives the URL of the App (say shared over email by a team member having view access), and tries to access the app, user will see the error as shown below pic. But user doesn't have a way to know the app maker or won’t have a way to reach to the maker of the app from the error screen.
Access error message on PA
When a user receives the 'It looks like you don't have access to this app. ....' ther is now actionable text "Request Access" that appears on the page which sends an email to the app owner to share the app.