That's not the case... what happened is they deleted the actual files themselves. On a computer when you delete files they arent really deleted, the bytes are just marked as able to be overwritten, the computer doesn't waste time actually flipping every byte to zero, so it just marks them as 'deleted' and later the computer will overwrite them with other things. By analyzing the raw memory itself you can usually recover these bytes before they've been overwritten. That is what happened, it was deleted, they just failed, forensic harddrive analysis retrieved each byte in the state it was in at the time of deletion.