Thanks for posting here in the Google Nest Community and sorry for the delay.
We understand your concern. When your camera’s video history was deleted by someone, all video history and snapshots recorded up to that point will be erased. Once your video history and snapshots are deleted, they cannot be recovered. We do not keep backups. To get to the Nest account that you have subscription to you just need to log in to that account in the Google Home app.
Check these helpful links for more information.