In order to protect your private files, all date added to Gallery Vault are saved and encrypted in your own device. If you haven't deleted Gallery Vault date or change phone, you can use feature 'Find Lost Files' to find them back in Gallery Vault Setting.
If it doesn’t help you, please follow the questions to find the answer:
What happened before you noticed that your content is missing?(Click to view the solution)
1) Format phone;
2) Update APP;
5) Delete the files.
Warm tip: In order to prevent your encrypted files from being cleaned by Anti-Virus software or cleaning software, it is best to link Google Drive to ensure that files are no longer lost.
Thanks for your understanding.