Used to have fun resuscitating files on magnetic media. It was also useful at times Windoze decided to fall over and die, at the time when the temp files were often readable.
Must look into how to do it on NAND flash memory, have precisely one photo accidentally erased, a happy scene outside Tokyo station.
The article is pretty crap, but the OP's comment about wear-sharing, it makes sense that a device won't really erase the blocks until there is no space where they are not LRU. Must check!
With flash mem., I think from too much of a writer-controller, not end-product level.