It's impossible to install the application again, because there is no trace about it on the available markets including Google Play Store. Look on your computer, maybe you have the APK file saved or backed up. Unfortunately, there is no way you can recover the photos from the locked vault without the main application. If the files are stored on an external storage, then connect the SDcard to computer using a card reader and then browse its contents. Locate the place where the files are stored, because it's possible that you can recover them using this approach.
