My friend that happened to me with my base at single player on March 2022. This issue is a bug that rarely happens in single player.

So do not worry. To combat this problem here are few ways.

Every time you finish your business in single player. Back up your save on the cloud (psn, Xbox , pc).

Avoid from swapping from from offline to online and from online to offline immediately. Instead exit to the main menu and pick the mode you want to go after starting the game while you are in main menu.

Use the admin panel to get what you want to restore.