Twice I have had people call me to tell me they found my lost disc at a course I have never played. I got the discs back a bit more beat up then when I lost them.
I got a call from Kentucky about a disc I lost at Fontana Dam (NC).
But by far the most surprising was the Cyclone I got when I joined the PDGA (ca. 1997). I lost it in 2003 or earlier. About 2 years ago some guys from Charleston, SC brought it to me, among some discs they'd dredged out of a pond. (That's 130 miles away, though I have played tournaments there). A testament to karma, and sharpies.
It still flies, though I have to say that Cyclones aren't exactly the cutting-edge disc they might have been in 1997.