There could be several reasons why your news item has disappeared from where you left it.
Was it spiked? Check the spiked items section of the workspace. Others have permission to spike items that you have created.
Did it expire? Ask the desk administrator to check the expiry limit for your workspace. If the item has expired, it was permanently deleted.
Was it sent to another desk or Stage? Check the other Stages in your workspace, or other workspaces. When an item is sent to another desk, the original desk does not keep a copy of it.