Well, I don't know what happened, but Esri uses a third party app for Community, and it's possible something went wonky and a spontaneous rollback happened on the server; I very much doubt someone has maliciously removed content.
I would note that this Community is not Esri Tech Support. If you want help from Esri, you should contact Tech Support according to the terms of your support contract. Community is a user engagement forum, in which some Esri employees also post, as fellow users.
Railing against Esri in the forums Esri provides for user interaction is probably not a good way to get help from staff contributors.
I've loaded tens of billions of rows into thousands of PostgreSQL tables in the past decade (a couple hundred million in the past week alone -- dev migration), many of which with plain vanilla ArcPy scripts and Python toolboxes into PostgreSQL databases without enterprise geodatabases enabled. There is a trick to it, though, and without details on the exact database in use, and how you've configured the database, logins, and schemas, and the actual load procedure you used, it's difficult to guess what may have gone wrong.
Good luck.
- V
