My youngest son's iPod is missing

. I'm 100% sure it is home, but just have no idea where. The last I saw of it was nearly a fortnight ago when I asked him to put it back in it's black and green protective case, which he did. Then I can't recall seeing it again.
We had grandparents visit that day, then he was quite ill for the rest of the week and it's just occurred to me that I hadn't seen it and he claims he can't find it...
Anyway, can anyone shed some light as to where they think it could be, please!?