When Kids Lose Stuff

I've written a discussion point over at the Brit Mums web site, but thought I's put it here too - to get your opinion about something:
So my 8 year old has lost his DS. He's only had it since Xmas but since we're traveling soon, it is a rather bad time to be losing it. We have traced it back to Saturday, when he went to a party (and dad took him, so it's not my fault.) We have torn the car and the house apart, and although I'm the kind of person who thinks things will eventually turn up, it's not looking too good.
What to do?
I don't want to be the kind of mother whose kids are so terrified that they lie about losing things. On the other hand, I know everyone loses things from time to time, and it's usually not done with any malice. However I also want them to know it's a big deal. Yes, we could probably afford to replace it, but I'm not going to. He needs to know that these type of presents are huge treats and not disposable.
A few years ago we bought the Queenager an I-Phone for Xmas. A huge deal although it didn't cost that much on our plan. On the VERY SAME DAY she lost her I-pad that we were going to give to grandma. Her reaction? It wasn't that bad since she now had an I-Phone. Gah! You can imagine how strongly I impressed on her that it did matter! (That one eventually turned up a whole year later, wedged between box spring and frame of her bed.) She recently forgot to take same phone out of jeans pocket when going to the loo, dropped it into the toilet bowl and is now craning to see texts since the light won't work! (We will probably have to replace that since she's off to college, but for now, she can live with the inconvenience of rubbish texting ability).
Anyway, lest I bore you all to death with tales of my careless kids, I was just wondering what anyone else thought of the right parental response when kids lose things