Since you've ruled out cloud services and hidden files as potential causes, it's important to consider other possibilities that could be contributing to this issue. One potential culprit could be a software glitch or corruption in the macOS system files.
To address this, you might consider running Disk Utility to check for and repair any potential disk errors or file system issues. Disk Utility is a built-in tool that can help diagnose and fix problems with your Mac's storage drive.
You can access Disk Utility by following these steps:
1. Open Finder and navigate to the "Applications" folder.
2. Open the "Utilities" folder.
3. Double-click on "Disk Utility" to launch the application.
4. In Disk Utility, select your Mac's startup disk from the list of drives on the left side.
5. Click on the "First Aid" button at the top of the Disk Utility window.
6. Click "Run" to begin the disk verification and repair process.
After running Disk Utility, restart your iMac and monitor if the issue persists. If files and folders continue to disappear from your desktop after this, there may be deeper underlying issues with your macOS installation.
In such cases, it might be necessary to consider backing up your important files and performing a macOS reinstallation or seeking assistance from Official Apple Support. They can provide additional guidance and assistance tailored to your specific situation to help resolve the issue with disappearing files and folders on your iMac desktop.