Took me a while to remember the name of Surrogates. Good flick, even if the compressed timeline of the future it presents is a little far fetched. One of the smartest sci-fi movies to come out in recent memory and I saw it almost by accident.
Um... do you mean 'Earth, Air, Water, Fire' or 'Earth, Water, Wind, Fire'... because those are usually the four elements used. I've never ever heard of air and wind in the same thing. Also, your favorite website Wikipedia(which is actually usually unreliable) says that the four stones are the four classical elements which are earth, air, water, fire. So yeah. I don't know if it's a typo or if I've misunderstood something or what, but here you are, my two cents.
It's a mistake. It was water and wind. They opened the stones at the end by blowing on one and dropping a bead of sweat on the other... and then of course the fifth element was Heart and after finding that Captain Planet shows up.