The encrypted files are stored in the folder .galleryvault_DoNotDelete_*** of all the storages of your device. They are in the top directory. (For Android 4.4 Kitkat, the folder in SD card is stored Android/data/com.thinkyeah.galleryvault/files).

Note: You may not be able to see the folder because the folder whose name starts with a dot is a hidden folder. You need to configure your file explorer to show hidden folders. 

There may be more than one storage in your device and the encrypted file will be stored in the same storage as the original file. 
For example, if you have an SD card installed in your device, you probably have two storages. If your picture is stored in the SD card, the encrypted file will be in the same SD card too.