Ha, I hear that. Been more then once I've gone into the parts room and find I'm missing a couple hot wheels as my 2 year old decided to raid the wall when I accidently leave the door open....although I try to discourage that as much as possible otherwise he would destroy them all. But in the end, they are .99 cent toys.
But whenever we go buy some, he gets to pick one out for his assorted collection as well and that keeps him ( usually ) happy to play with. Although I will say, hot wheels suck even more then legos to step on in middle of the night in the dark....