Ah... the frustration...

Ever have the perfect plot- all the settings, sub-plots, and characters laid out, but there's one itsy bitsy key part that you can't figure out??

That's the situation I'm in. Let's just say my characters have to find something. I know where they're gonna find it, and I know when. I just don't know how.

Anyone have any ideas?

Just daydream. It'll come to you.

Leave the idea alone for a couple of days. Then think about it some more. Then leave it alone for a couple of days. Then think about the problem some more. (rinse repeat). This is how I solve problems; I'm not sure if it will work for you, but it generally works for me in story plotting!

Maybe you're thinking about it too much?

Combination of what Snoink and aeroman said. I often do a lot of random daydreaming, and I get a lot of cool stuff out of it. 95% of those thoughts have absolutely nothing to do with my currents story, but one things lead to another and I eventually get something. So, yeah, what they said. They just beat me to it.

Something I forgot to add, make sure to not stress about it (unless you have a deadline then I would probably stress it). But answers don't always come easy for plot problems/holes. So like I said before, do that. And make sure you're not stressing. (everyone stresses a little bit, but if you do it too much than you're going to end up wanting to rip your hair out over the problem)

I've had the exact same problem. It just came to me one day, in a dream. One day, it will happen to you too, hopefully. If it doesn't, you'll find a way, writers do that.

Mix what everyone has said, and shake well.

Don't fret about it. Nothing blocks ideas like fretting. It will probably just come to you, if not then you might like to fiddle with the circumstances a little. THen you'll have a slightly different situation to wonder about, and that one might spark ideas.