I don't see how we can help you find it.
Do you keep it anywhere normal?
Anyone else who might have borrowed it, siblings, friends?
If you can't find it, can't buy another one, why don't you ask your friends if they have a copy that you could borrow.
I say this because, for some odd reason that I never understood, once my Sims 2 disc was installed on my computer and my brothers computer, it would play without the disc in.
I don't know if I had unknowingly fully installed it onto the computer or whatever, but for whatever bizarre reason, I could play the game while the disc wasn't in.
Might happen to you, if not, atleast you can maybe play it for a bit.