ICloud and photos.
I recently cracked my iPhone screen to the point it wasn’t useable. I switched my SIM card to my old iPhone to use in the meantime. For whatever reason though the photos on my iCloud from my cracked phone were somehow put on the old phone, and deleted all the photos that were Stored on my old phone. I have no clue what happened to the. And they were very important! I have no backups.
iPhone 7, iOS 13