How can this mysterious sound come out of a D guitar chord? Sounds like a high-octave FA.?

I was trying to play (trying because I'm no good) the Zephyr Song by the Red Hot Chili Peppers, and noticed that I emulated that last chord quite well (just an ordinary D)... But that high FA sound isn't in any of the simple D chord I struck? WTF? How can it happen? Someone explain this to me? Not really good at acoustics (or music for that matter)