The Google Maps Timeline has long been a useful though slightly uncomfortable feature that maintains a complete record of everywhere your phone goes (and probably you with it). Google recently changed the way it stored timeline data to improve privacy,

Google deleted the Timeline data for many of its Maps users. If you had a backup enabled, you should be able to restore that data, but otherwise, it's likely lost forever.

Google Maps users have recently been complaining on places like Reddit that their Timeline data — the app’s historical record of where they’ve been — had disappeared. Now, Google has confirmed to Android Authority that it accidentally deleted the data and that anyone who wasn’t using Google’s cloud backups is out of luck.