Casper has now moved from http://uselesscode.xyz/android/casper to https://casper.io
The Casper application package name and media folder has also changed from xyz.uselesscode.casper to io.casper.android
If you have just updated to the new version, you will be prompted to uninstall the current version of Casper, and the media folder will automatically be renamed.
Once you have uninstalled the old version of Casper, you will need to reboot your device for it to automatically refresh the Gallery app.
This must be done, otherwise the saved snaps in the gallery will point to files that have been moved.