What about those of us that actually deleted Facebook after the scandal? How are we supposed to check if our data was shared with CA if Facebook requires you to be logged in to check?
Clearly there needs to be some line drawn, like not permanently keeping an archival of all information shared with Cambridge, as that would potentially cause more harm than good. Yet, knowing how many people were affected, and being able to identify if you were one of them, seems a permanently useful thing.
This of course is a bit idealist, I'm just answering the question on my idea of what should be done - not what will be done. Tbh, I'd rather see that data be held by some government entity and not FB at all, but I'm not sure who that would be, if they exist at all.
(FYI, they probably know your phone number and who you made phone calls to, when, and the durations for the last 5 years)
If you're actually very curious, all I can think of is you could ask your friends if any of them had their info leaked, and if it was through themselves or a common friend. If you're friends with anyone who gave access to the app, you're part of the bunch.