My children used to quite often lose (or chew) the small pieces of sets and it drove me crazy, especially when they were items that couldn't be easily replaced through the DS. I felt like a very bad mum always reminding them to be careful not to lose stuff whenever they were playing. 
I have lost a batch of bagged red Maltese knight figures (half a dozen, I think) in this house several years ago. I keep thinking they'll turn up one day, having fallen behind a cupboard perhaps or into the wrong box, but so far no luck!
Hi
Isn't is funny how trying to teach responsibility seem to be mean

We as adults (not including myself of course) seem to think that kids do not value the toy if they do not care for it as we do
I would wish you "good luck" on your search but after 2 years I think you may need a little more than luck now. Maybe just "dumb luck" will find them
Rasputin "The Mad Monk"