Call me selfish, but I do not loan items at all. (except family) I lent a video to a friend once, when I got it back the cover/box was all mangled. Her child got a hold of it was her excuse but my thought is: "put it somewhere where the kid can't get it. Take a little better care of it because it does not belong to you" Same thing with books. I am very easy on my items and my read books still look like new.
It's kind of hard, you don't want to teach your child to be selfish but as you can see not all people are very considerate and/or considerate of other peoples property.
I hope you get your game back and do be careful about who you loan to.