... don't leave it in a place where a random disaster (or random disgruntled third-party employee) can wipe it from the face of the Earth. Terabyte-size drives are cheap nowadays. Buy them. Buy many of them. Back up elements to them on a regular basis. Don't destroy raw material until the editing is done and the master has been copied at least twice purely for long-term storage, never mind how many copies need to be made available for distribution. Don't even rely on just hard disks - dump masters to tape if you can afford it. HDCAM's not completely overpriced; hell, even standard-definition Digital Betacam is better than, quite literally, nothing.
If they're lucky, the animated contributions and sound elements may be retrievable should the individuals responsible for those be more scrupulous about their material retention than the studio (the story didn't quite make clear what, if anything, they've been able to recover), but any location shooting lost is going to be a pain to redo.
This should be a very expensive lesson for their technically-inclined production crew and, if they have any, actual IT staff.