Deleted Chatter Groups and Feed Posts are unavailable for recovery through the Recycle Bin, and they cannot be accessed through the Export All function in the Data Loader.
This article explains why deleted Chatter Groups and Feed Posts cannot be recovered and describes available workaround options.
Chatter Groups and Feed Posts are hard deleted in the organization. This means that they bypass the Recycle Bin and are permanently deleted.
Workaround: Recreate via Data Export
If your organization utilizes Data Export, and includes the following objects in the export, it may be possible for you to recreate the groups and posts with Data Loader:
If you would like a workaround, here is a conversation in Answers where users talk about possible 3rd party applications in app exchange Can you prevent certain users from deleting chatter comments/posts?
Please review: Support for third party apps, installed packages, or programs
To upvote the Idea to prevent users from deleting a Chatter post, you can review Prevent the deletion of Chatter.
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