As it turns out, that's just what it was.
A band called Rogue Wave did it for the "Music from the O.C. Mix 6 - Covering Our Tracks" compilation. While it's certainly not going to replace the original, I found it pretty interesting, almost like a totally different song: smoothed out a lot, a little Shins-y (although the vocals aren't like James Mercer's at all). Here they are playing it live (courtesy of You Tube).