Each Device That Has a Microcontroller / Controller To Run It And Has NAND / NOR Memory Chip To Store Data And it Can In The Passage Of Time Get Weak " I Mean The Cells Inside " Can Get Weak  .When This Situation Occurs You Will Have a Device Thats Working Fine But Your Data Is Not Accessible  .We Can Recover Data From Such Situations By Using Progessional Grade Data Recovery Tools .Genrally We Do a Pretty Good Job With This Kinda Failure .