Hi KH_4655,
The most common reason for items to be removed from a device without your direct request would be if the storage is critically low. iPadOS and iOS will free up room by removing items that can be redownloaded if necessary. To check your device storage go to Settings, then General, and tap on About. Your total device capacity and available storage will be listed there.
If too low, How to check the storage on your iPhone and iPad offers these tips for managing it:
"Use recommendations to optimize storage
In the Storage section of Settings, your device might offer recommendations for optimizing your storage. To optimize your storage:
- Tap Show All to see all the recommendations for your device.
- Read the description of each recommendation, then tap Enable to turn it on or tap the recommendation to review the contents you can delete."
Regards.