They swiped your camera roll after you handed over the phone
Do not hand an unlocked Photos grid to anyone. Use Guided Access for a single image, or share a copy. Keep private media in Blopman so a swipe cannot reach it.
In the moment
Guided Access (Accessibility) can pin one screen. Or AirDrop/share a single export.
Prevention
Private shots should not live next to the cute dog photo in Recents.
FAQ
Does locking Photos app with Face ID fix this?
It helps when the phone is locked. Once you unlock and open Photos for them, swipes still work—vault private items.
Try Blopman
Local encrypted safe for photos, videos, and documents. No account. Free + lifetime Pro.
iPhone / iPad: available on the App Store. Android: not on Google Play yet.