There could be several reasons why your highlights disappeared from the Adobe Reader app on Android after they were saved. Here are a few possible explanations:

1. App or device update: If you recently updated the Adobe Reader app or your Android device, it's possible that the update caused some compatibility issues or resulted in data loss. In such cases, the app may not be able to retrieve your saved highlights.

2. Syncing issues: If you have enabled syncing across multiple devices or cloud services, there might be a problem with the synchronization process. It's possible that the highlights were not properly synced or that there was a delay in syncing, leading to the disappearance of your highlights.

3. File corruption: If the PDF file itself is corrupted or has become inaccessible, the highlights associated with that file may not be visible. This can happen due to various reasons, such as file transfer errors, storage issues, or incorrect handling of the file.

4. Storage limitations: If your device's storage is running low, it could impact the functioning of the Adobe Reader app. In some cases, the app may not be able to save or display highlights properly due to insufficient storage space.

5. User error: It's also possible that there was a mistake or misunderstanding during the saving process. Double-check if you followed the correct steps to save the highlights, as any errors or accidental actions could result in the disappearance of your highlights.

To troubleshoot the issue and potentially recover your highlights, you can try the following steps:

1. Update the Adobe Reader app to the latest version available on the Google Play Store. Developers often release updates to address bugs and improve app performance.

2. Check if the highlights are visible on other devices where you have the Adobe Reader app installed. This will help determine if the issue is specific to your Android device.

3. Ensure that your device has sufficient storage space available. If it's running low, consider freeing up some space by deleting unnecessary files or apps.

4. Try opening the PDF file in a different PDF reader app to see if the highlights are visible there. This will help determine if the issue is specific to the Adobe Reader app.

5. If possible, try reinstalling the Adobe Reader app on your Android device. This can help resolve any potential app-related issues.

6. If none of the above steps work, you may need to reach out to Adobe Reader's customer support for further assistance. They will have more specific knowledge about the app and may be able to provide additional troubleshooting steps or insights.

Remember to regularly back up your important files and highlights to minimize the risk of data loss in the future.