Lost logic board screw nut, where to get it?

While putting the iPhone 4 back together after replacing the front screen assembly, I lost the nut from the logic board for a screw.

Explanation:

iPhone 4 install guide

See guide above, it's the yellow screw in Step 13, I still have the screw, but the nut that holds it just jumped out of there and got lost, the same nut you can see in Step 8, holding the orange screw. That one seems pretty solid, so can't imagine how it could get out, but it did.

Any ideas where I could get one, or what I can use instead. I think that nut makes a connection of some sort.

My iPhone now is overheating around that region, near camera, and wouldn't start, except a couple of times, but then I turned it off and disconnected the batter, for the fear of damage.

Any help or ideas appreciated. Thanks