3gs exploded diagram anyone?

I replaced the power flex cable in my iPhone 3gs and have somehow ended up with a spare screw, but have no idea where it lives. Everything works fine, so it's not vital, but I'd like to find where if only to keep the tiny thing safe.

Hoping with an exploded diagram of the phone, I can work out where the screw has come from.

(As a side note, I'm sure I found a really good guide on here for replacing the power flex cable, but can't find it for love nor money now. The proximity flex is listed under the 3GS guides, but not the power flex. Might be worth listing so it's easier for others to find.)