Photos in photo vault automatically deleted?

I have a photo vault app on my iPhone (a secret app to import your important photos in with a password locked) and recently I opened it up to recheck a photo but then all of my photos that I imported are now gone. I checked everywhere on my phone and there was nothing. It was like these photos were automatically deleted without my permission to being deleted in the first place. I did not lend anyone my phone nor did I accidently clicked on something. It just poof… Gone. Any reasons? Mystery? I believe contacting support for this app would be useless.

Photos that contain criminal activity are required by law to removed from the users device and sent directly to the FBI. See you in 20 years.

Which app? Ask the developers?