We didn't know that it was lost until it was recently found by George's son Dhani, Sir George Martin, and his son Giles at Abbey Road Studios. (More here.)
Though I think the solo - which sounds like it was lifted from "The End" - clashes somewhat with the soothing, warm-breeze feel of "Here Comes the Sun," it's still cool to hear.
Watch and listen:
(If the video is removed, go here.)