Google has confirmed that it accidentally deleted historical location data, also known as Timeline, from some users’ accounts. The issue affects only those who did not enable cloud backups. Google warns that users without backups cannot recover lost data.
According to a statement by Google spokesperson Genevieve Park, the technical issue caused the deletion of Timeline data for some people. However, nearly everyone with encrypted Timeline backups can restore their data. Users can check if they have enabled cloud backups by tapping on their user icon and looking for a cloud icon in their Google Maps app.
Google previously warned users that switching to on-device storage for location data would mean that location history could be lost if not backed up. While users can export location history data, there is no obvious way to reimport the data without using the cloud backup servers.
Source: https://www.theverge.com/news/634442/google-maps-timeline-data-deleted-cloud-backup-recovery