Need help: Are we in the "wrong" in this situation? -see details?

Okay, lets say you have an almost 3 year old. You ask your parents to watch him while you run out for an hour.
You put a short movie on your laptop, so you can get dressed..all the while you are supervising your child.
You put the laptop in the living room, and tell your parents you are leaving. One parent comes upstairs (has to move a car so you can get your car out) So your child is left alone for only a couple minutes with laptop.
Said parent comes back inside and goes downstairs, leaving their grandchild with laptop.

They then come upstairs and discover the grandchild has ripped apart the keyboard to the laptop. They never made any mention of it to the parent of the child, until they came home and they were questioned.
Laptop has a warranty, and goes to get fixed. Turns out, it’s been fixed too many times, and legally they say it’s a lemon and refuse to return it. Were told when taking it to be fixed that it’d be an easy fix, no need to back up information.
So, laptop with all information is gone, but can possibly pay to get the hard drive back, it’d be a hefty amount.

Now, regardless of the fact that owners of the laptop should have backed the information up (even though they weren’t informed that they may never see their own laptop again…), if they have to pay a hefty amount just to get information off of the laptop (which might not even be possible, according to the fine print) Should the owners of the laptop (and “owners” of the child) who ruined the laptop, have to pay for it all? Or the ones responsible for the child when the destruction occurred?

Or, is this a “live and learn” sort of situation?